I enjoyed Riverdale. I would never want it to replace a Star Trek show. A teen drama with Star Trek dressing absolutely stinks of desperation from Paramount.
In 1997 adding a sexy Borg crew member to Voyager reeked of desperation. But the writers actually gave a shit and whoever was in charge of casting took the time to find someone who could actually act, so in the end Seven Of Nine became one of the best things to come out of Voyager (nevermind the cringe worthy marketing and costume).
End of the day, I don’t care about the mental state of the exec signing off on an idea, because even a bad one can turn out good with the right talent. And I don’t see why Star Trek as a teen drama is a bad idea. Star Trek can work with all sorts of genres, and we’ve still got SNW holding down the fort as the old school exploration series.