I understand the fact that investors should do their research before investing into any project or coin, but MarketCap sites, such as, CMC, CoinGecko and the likes, also have some roles to play.
Reputable exchanges do screen and scrutinize every coin that is listed on their sites and peradventure there is any already listed coin found suspicious of scam, it will be delisted. With this, i also expect that MarketCap sites should do the same, but these days, it seems they are left and displayed without doing the needful.
If this is done with due diligence by deleting or delisting scam coins, it will go a long way to help the system and at least make it safe to some extent.
I agree with you, since this platforms are very useful in terms of data and insights. They must observe transparency and professionalism with those things such as execution on truthful information about the platforms they want to list on the site. This is so important to avoid further problems regarding faked and scam front projects to be listed.
As problematic as it seems they really not giving any attention to this kind of thing, they are only listing the most demanded coins whether it's implicated as a fraud or not. The unpopular ones will be left behind and will eventually get delisted even if they are legit. Even I've seen tons of crypto that works on ponzi scheme listed there, not a new thing.