I think there are many altcoins that can be used as investments at this time, but we must be able to do research independently about the altcoins we will buy, so that it can have a positive impact later, I personally choose altcoins that are included in the top 10 CMC, because after I researched coins that have market capitalization has a greater chance of increasing in the future, and good altcoins to reference are ETH, BNB, Solana, Polkadot and Cardano.
You are right, making altcoins an investment is not wrong. Currently, there are many altcoins that are growing quite well and many are included in the list of the best rankings in CMC/CG, indicating that altcoins are worthy of it.
but analyzing well from the market cap is certainly highly recommended also from the graphs that occur in daily movements because it may indeed not develop well and should be avoided as an investment.
I agree with what you said that altcoins that are suitable for investment such as Ethereum, ADA, DOT, BNB, SOL and of course with newly growing altcoins such as LUNA, AVAX which have the potential to be able to give a surprise.