No definitely most of these coins are not needed. One could argue only a handful are actually needed. I mean for 99.9% of them they are just clone coins that are all marketing and no substance.
If you think clone coins or similar coins are not needed, then only Bitcoin can be accepted. You should understand the name first, altcoins = alternative coins, what does it mean? Those are alternative options besides Bitcoin. But although they are alternative coins, they should have a role, have a purpose, and have functions. Can you imagine if only Bitcoin survives in crypto market? I doubt it can have big supports like today.
Only Bitcoin is not enough for the market, as like you said, altcoins surpass it in many positions. Some altcoins are faster, others are more private, all of them are cheaper etc. Moreover, bitcoin can’t show increases of 10 times or more in the short term. Nevertheless, altcoins are capable of increasing by 100 times easily, so they are more attractive for traders.