I have been using those covers for a while now when I don't have the money to commission one. The best part is, you can still get readers with only words on a cover. My own books have done it, and I have seen others hit trending like so.
The idea of attractive covers being the only decider is a massive cope for people. Sure, it does make a difference, but it's not everything. It will get your foot in the door faster, but it doesn't keep you in there.
It didn't work.