It will be pretty confusing if someone goes for the top 100 in the list of cryptocurrencies listed on CMC because when you go for choosing the altcoins you want to invest in, you will need to thoroughly evaluate the coins and tokens and the projects behind them so that you can choose the best ones and your investments don't go wasted. That's why, one should narrow down that list and then go for choosing how many they want for their investments.
Indeed. There are too many options if we consider the top 100 in CMC. Among the top 100, there are still many weak altcoins. It will be too risky for a beginner or for someone who has lack ability in analyzing the potential coins to invest in. Moreover, it will waste time if we analyze too many altcoins. So, I agree that we need to narrow the number of the altcoins. The top 25 is enough to be the option for a beginner. But make sure to ignore meme coins and stablecoins.
If the investor is a newbie, I would suggest they go for the top 20 or maybe 30 and evaluate each one of them very closely and research about them and see how they have been doing in the near past just to have an idea about their recent performance, and then choose the best ones among them.
Top 20 is enough, there are already many altcoins to choose. When I was a newbie, I only focus on the top 10. I don't think too invest in too many altcoins, it is enough to invest in 2-3 altcoins besides we invest in Bitcoin.