Sorry, there is nothing in the medium link that you posted that suggests that Coinbase is scam! Sounds more like clickbait to me!
Maybe you have missed this part? I am pretty sure that it is suggesting that Coinbase is turning into a scammy exchange:
Bug in Coinbase systems prevents some exchange users from withdrawing funds
Technical issues led to the inability of some of Coinbase’s users to withdraw their funds. The issues, however, did not cause any exit scamming accusations
Even if that event did not cause any exit scam accusations, it is hinting that coinbase is a scam based on the author's way of presenting the news.
They would have to tell that they would list a certain coin and people will start to pump and dump it.
People pumping and dumping coins is not coinbase's fault, it's the opportunistic traders who make the call. Upon reading the article on the OP, I have concluded that those 40 coins coinbase is planning to add are not that much of a shitcoin and most of them can have a real world use cases in the future.