It sounds so ridiculous for anyone to invest just because a coin is on the top list on cmc, that's the worst investment decision imo.
Invest in a project base on quality, standards and team, it can be a new or already existing project but it shouldn't be because of the top 100 list, the position is not permanent.
If they choose the coin without analysis, it is not a good decision because we know that the coin on the top of the list will surely be replaced by another coin that can get more support, and the project has more opportunities to develop. But if he chooses a new project, he has to look for more info because he has no idea what will happen to that new project in the future. Perhaps, we can suggest he buy bitcoins instead of altcoins due to the change in coins at the top of the list.
It's really hard to find an altcoin that will last longer and can make it to the top and even though they are in the top 10, they can still fail if they make a mistake like the LUNA. And, it is like you are playing with our knowledge and only predicting which can make us more profit in the future.
That will happen if you don't know which altcoin will replace the altcoin in the top 10 list. We can be wrong in predicting or analyzing, which can make us lose the opportunity to profit. But if you invest in bitcoin, even though the altcoin position will change in the next altcoin season, the bitcoin position will still be above the altcoin, and you will make a decent profit on bitcoin.
Perhaps, if you want to choose an altcoin, try to follow the project's journey so you can see the differences between each altcoin. It can add information to your analysis. But that also can't be a guarantee because we've already seen what happened with LUNA and FTX.