The better question here is not 'what is the point', but why us the UN Security Council designed in this way.
The answer to that comes from the close of the second World War (actually you can go further back to the League of Nations and WWI, but lets keep it simple). Who were the major powers of the victors of WWII? Why it turns out to be the same list: the US, UK, Russia (Soviet Union then), France and China.
As the victors they had the power to create the United Nations in their image. The veto power was part of this. Since they were the victors they got the greatest power.
Now of course, as you mentioned, this has severe flaws. It is inherently unequal. It leads to situations like Russia and Crimea, or Russia and Syria. It is also locked in time; if one of the nations loses its great power status the security council may not reflect that (and some argue that some of the nations on the list are not as powerful as they once were).
For all of these reasons there are of course cries for reform. There are many different proposals for this. Some say that new permanent members should be added, like India and Japan. Others say that the entire system of permanent membership is inherently flawed and it should be switched to a majority vote system like you mentioned.
As for a standing UN army... well, there sort of is one: the UN Peacekeepers. It's not exactly a standing army for the UN, as the UN is nationless and the participants in the army are from a nation, but it is a force that has weight. It has 124 participating countries with over 105,000 personnel, making it the 45th or so largest military in the world. That might not sound like much, but it is equipped well with lots of tanks, aircraft, and ships. And more importantly if a need would arise they would receive massive support from UN members (such as US support in Somalia).