They can’t actually stop you from covering it (at least in the US for non-dramatic music)
https://en.m.wikipedia.org/wiki/Compulsory_license
Of course you have to pay royalties.
There's almost zero-reason for a record label or artist to turn down a kids bop cover if Kids Bop thinks they can rewrite it to work for their exclusive audience.
I can barely believe I'm reading this.
I mean, of course many artists would allow it, but it should be obvious that many wouldn't consider it for a second.
You do realize there was a time when artists wouldn't allow their music to be used in commercials, and this kind of thing, right? Completely distorting a bit of art for the 'target demographic' is usually way out of most artists' area of interest.
I could also see some artists just saying "No, this song is about drugs and sex; you can't cover it."