The purpose of Altcoins according to my short knowledge is just to make things easier. This means that when people cannot afford to buy Bitcoin because it is expensive, then Altcoins are another option for people to invest. What is happening now is that many people make the wrong decisions when buying coins.
I don't agree with you. You can buy a fraction of a bitcoin, so if you can only afford $100 of BTC, then buy $100 of BTC if you believe in the crypto.
Alt coins, in my opinion, try to solve an issue that BTC cannot do or is to expensive to do. Healthy competition is also great.
ADA is trying to compete with ETH with smart contracts. One might fail, both or both will continue to grow.
I am looking at new projects like BYG that actually have use in the upcoming decentralized NFT "game" Black Eye Galaxy. Holding assets in Black Eye Galaxy can actually bring you high gains. Those are the type of projects I look at. Projects I can understand and see how they work. You should check them out.