It is, but not for that reason.
The numbers are not actually hard to come by; in the late 70s for example, Congresses enacted 700-800 laws; by the 90s that number was 400-600; the 10s so far have seen numbers in the 250-350 range so far and that includes the current Congress which has been characterized by a single party controlling both chambers of Congress and the presidency. See https://www.govtrack.us/congress/bills/statistics . So the passing of legislation has become surprisingly harder.
One could also validate the suspicion that the Senate is slower than the House at approving legislation, but I think that would be a really dicey effect to characterize. For example, if one is doing it by the number of bills passed, one will naturally run into the problem that the House has many more legislators than the Senate. One might compare probabilities of "it passed the Senate given that it was introduced in the House," vs "it passed the House given that it was introduced in the Senate" for example. So for example I can tell you that of the 281 enacted laws of this current Congress, Senate bills make up 87 of them while House bills make up 194 of them. This sounds like a big difference until I tell you that the House has introduced in various forms 8,663 bills compared to the 4,541 bills of the Senate and so the probability of a Senate bill making it into law given that it was introduced is 1.9% whereas the probability of a House bill making it into law given that it was introduced is 2.2%, and it hardly seems like that's a significant difference to quibble over. There might be a more meaningful difference if we limit it to bills that really have been seen by both houses, in which case there were 237 House bills there to 250 Senate bills, but those numbers coming close to each other is bad for the hypothesis, since it means the opposite -- that Senate bills tend to more often get to the House than House bills get to the Senate, but that once they do, the Senate bills tend to die in the House more than the House bills tend to die in the Senate. But I would need to characterize the numbers for much more than just the present Congress to see (a) is this even really the right number to be looking at? and (b) have these probabilities really changed over history or am I just detecting "how the system works" and not "what's different today than in the past".
So I'm not sure that one can really come to a strong belief that the Senate is moving too slowly and it's making the House ineffective.
Maybe it's the House what has to change
The bicameral legislature we have comes back to an ancient debate in the US: should the constituent political body be the people of the United States, or the states of the United States? The solution was just to be extra-conservative: "something should not become a law unless both approaches agree that it should be one." So we get two representatives from each state in the Senate and we get roughly proportional representation of each state in the House and the House tends to better represent the urban city concerns whereas the Senate protects rural and states' rights better. If you still believe that this is a valid concern -- that the US government should be somewhat weaker and that state governments should be stronger, so that our politics is a bit more heterogeneous -- then it doesn't make much sense to change the Senate: it has to exist and it has to have first-past-the-post elections because there is only ever one seat "up for grabs."
The House's purpose, however, is not served all that well by the House's structure. The House is meant to ensure that every person feels their will is heard in Washington, but the House faces several biases that have to do with the way territory is carved up into districts. First, there is still a systematic bias towards state representation because states which would be too small to qualify for a representative still get one; second there are many US citizens who cannot have representation in the House because they for one reason or another do not occupy a state for its purposes (Puerto Rico, Washington DC); third there is a well-known process by which the local governments of the various states choose "districts" to run first-past-the-post elections in, and they choose those districts so as to maximize the chance that some candidates retain their seats, a process called "gerrymandering" after a political cartoon depicted one of these districts, made by Massachusetts governor Eldridge Gerry, as a dragon or salamander in its contortedness.
The thing is, precisely because the Senate exists to protect the states, there's no reason that this districting needs to be done in the first place. There's no reason that it can't just be a proportional system.
See I think the early US assumption was "we are a bunch of very independently minded strong personalities and we expect that US politics is always going to be that way, so we do not need to consider the influence of political parties." This assumption was wrong in practice: political parties have absolutely dominated the political discussion in the US for basically its entire history. So I think that the central struggle revolves around giving parties a central place in the political system rather than tacking them on at the end, where they get an unreasonable amount of political power but are also unreasonably vulnerable to infighting.
What a different system could look like
Other countries have a parliament system that works like this: the parties of those countries are real established political entities in their political process; they need to specify "here are the people that we will put in office if you vote for us." The people of the country vote for the parties that they want; if the House is fixed to 400 members, say, and a party gets 30% of the vote, it can expect that the top 120 names off of its list will be representatives. And you just don't need to worry about apportioning this among all of the different states in any way, because the people were represented (they got to sway the party composition of the House) and the states were also represented (they got to sway the composition of the Senate).
The reason that this would be desirable is that perhaps the actual reason that legislation is dropping, has to do with the two-party schism in both the House and the Senate. In my limited experience, US citizens are neither Republicans nor Democrats; everyone has a party who they vote for but nobody likes their party, they are just terrified of the other party and they can't take the risk that the other party gets into power. This leads to a widely recognized effect where voters are encouraged, over and over, to not vote for a third party in any sort of political race because those votes would be "wasted."
So the first two years of Trump's presidency have been rather low-legislation even though they featured party domination, and my best guess for why that is has to do with the internal conflict of a Tea Party movement against the more polished traditional-GOP movement. And my solution is basically just, the Tea Party should be an actual party, same as the Green Party and the Libertarian Party are. It can't be, right now, because it enjoys enough Republican support that it would cause the Republican party to lose elections if it weren't a minority sub-party in the Republican party. But if you just have the people vote on parties, then the Tea Party becomes its own political entity and it has some separate agenda from the Republican Party and it represents its own concerns in the House -- and on the subjects where they agree they still work together in the House; and on the subjects where they don't agree they have to form different coalitions with other small-government parties like the libertarians, say.
The lasting effect on the Senate is harder to calculate, but Senate candidates would probably no longer belong to just one political party. You might find out "Oh, the junior senator from South Carolina is affiliated with the Libertarian and Republican and Green parties: now that's weird, a small-government traditionalist environmentalist."
What it does make much less clear is the presidency since the electoral college still depends on that apportionment of representatives. But there are options there. The most radical is what other folks do with their parliaments -- the parliament simply elects the executive branch directly. But if you wanted to preserve that classical separation of powers, there's no reason that you couldn't leave the current apportionment steps in-place and just have it not used for the House at all.