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.
So the culprits of this whole situation are investors who for one reason or another give their money to projects that are subsequently useless for the market.

As a rule, the reason for investing in such projects is financial interest. Look at the list of top coins.
A huge number of mediocre projects received their funding from us. The problem is not in bad projects, but in people who invest in them.