On the Discover page, just now, I found 10 good posts among the last 50 posted. 40 out of 50 were trash spam posts! And all of them were from low-rep newly created accounts.
In concert with @Sardart's suggestion in a recent @Colleen Ryer suggestion (here) to limit posts to 1 per day for accounts with 50 rep or below, 2 posts per day for accounts with 80 rep or below, and 3 posts per day for accounts with rep above 80, I offer the following suggestion on top of that brilliant suggestion ...
Automatically block accounts with rep below 20 if they have 5 posts reach a low-quality score. Lock them so they can't be used any more. In order for those accounts to be re-activated, the user should have to file a petition to the Tribunal for an account review and prove they aren't spammers/plagiarists.