Is more [Congressional] business decided by inaction now?
Not really. It has been the case often that members of Congress will introduce legislation, particularly amendments, they know have no chance of passage; but do so more to express their views and build their credibility within their faction of their party. These amendments are sent to committees where even members of their own party will not take up the proposal.
Following is selected data about legislation introduced in Congress. Only those proposals that may become law are included.
Introduced Passed Became
Congress House Senate One House Law Years
116th 8946 5034 548/146 193 2019-December 2, 2020
115th 7547 3874 624/122 443 2017-2018
114th 6644 3589 507/ 78 329 2015-2016
113th 6024 3067 349/ 75 296 2013-2014
105th 5014 2715 219/159 404 1997-1998
104th 4542 2264 197/145 337 1995-1996
103d 5739 2801 229/165 473 1993-1994
95th 15587 3800 286/217 803 1977-1978
94th 16982 4115 263/233 729 1975-1976
93d 18872 4524 223/264 773 1973-1974
Note: The two figures in "Passed One House" are the total of bills and
joint resolutions passed in one chamber with no action in the other.
Given as House/Senate.
Data source (requires multiple searches)
It appears, based on this selected data, that the House has recently and increasingly passed more legislation that is not considered in the Senate.
Another table with a slightly different view may be found at Statistics and Historical Comparison.
Since World War II (the earliest we have data), Congress has typically enacted 4-6 million words of new law in each two-year Congress. However, those words have been enacted in fewer but larger bills. Therefore, the generally decreasing number of bills enacted into law does not reflect less legislative work is occurring.
List of United States federal legislation shows counts since 1935 for laws only and reflects the trend toward fewer laws, as mentioned above.
With regard to appointments, there are literally thousands of appointments in any given year to which the Senate gives its consent. For the most part, these are advancements in grade or sensitive assignments for commissioned officers of the military and some civilian employees and judges. It is mostly the high-level appointments (related to the cabinet and notable commissions and courts) that attract press coverage.
The other criteria are "too hard to track" and, therefore, cannot be distinguished; particularly since some, going back to the mid-50s (from a comment), would have occurred before the internet.
Is this happening more often now than it did in the past, or is it more widely talked about now, or was I just not paying attention before?
Apparently "happening more often now", though admittedly more data might reveal other periods with such "inaction".