Why do you think exchanges are still listing shitcoins? Do you think there are some advantages to having a bunch of shitcoins on an exchange?
Exchanges are willing to list clear scams with fake teams and plagiarized whitepapers, let alone "legit" shitcoins, and only reason is money, and ignorance of average crypto investor.
The main problem is not that exchanges place bad coins on their platforms, but that such coins generally enter the market.
Indeed, without proper funding, the project will not have money even to pay for listing on a bad exchange.
I don't think that's necessarily true, that shitcoins are still listed on the exchanges because they managed to raise a lot of funds. Back in 2017 this was probably true, as basically any shit project managed to raise few million USD, but situation changed now, and most of the projects never comes even close to reaching soft cap.
Shit projects are now capable of doing IEO and getting listed for a few BTC, and they are willing to invest their own money into it as they know that they will manage to get their money back and make nice profit by unloading their worthless tokens/coins onto clueless traders.