CoinGecko is just an informative site. They are right in detailing every cryptocurrencies of the market indiscriminately. There are no issues by doing this, especially because they display a warning message on the top of the screen. We could argue the message should be more highlighted or the text more emphatic, but scams are also part of the history and shouldn't be forgotten or ignored. Instead, we should learn and keep them alive in our memories to not fall for similar offers in the future.
This is my posture as well, do we want those websites instead to cover the truth and to not report coins like that? This will be incorrect as we need to know if there are still some exchanges and traders that are interested in a scam coin like that.
Also this would make things way more complicated for sites like that as now they will have to evaluate each coin and determine if it is a scam before they report anything about it, and this is something that they will have to do every single day as we know that coins that seemed legitimate can turn into a scam at any moment, so doing something like that will only bring them headaches while bringing no benefits to them at all.