I’d say that Madonna’s remake of “American Pie” was the most useless remake ever. Radio stations were bombarded with requests to NOT play that song.
I think Donna Summer discofying MacArthur Park is just about as bad, (CHINESE checkers?! Was that even necessary?) but since my wife likes it, it’s by definition not as bad as Madona’s. 
About 4 years ago, 5 Seconds of Summer did a cover of Queen’s “Killer Queen” that somehow got airplay on adult contemporary stations. The song deviated very little from the original, with the obvious exception that the vocalists’ talent level was far inferior to Freddy Mercury’s.
Here’s one that fits the OP TO A T:
Let’s go to the way-back machine about 40 years. David Lee Roth thought he could do better than Van Halen, so he went solo. His version of California Girls sounds exactly like The Beach Boys (down to using many of the same musicians), except he added in a few yells every so often. Absolutely f-ing useless.
I don’t mind covers in general. I don’t know if Joe Cocker ever wrote anything, and Linda Ronstadt’s most famous numbers were covers. The more I compare Carlos Santana’s versions to the originals, the more I hear the original with improved guitar work. I’ve lost some respect for him.
I’ve heard that one a couple of times and I completely agree with you. Why would stations even play it?
McArthur Park is, perhaps, one of the worst songs ever written; certainly has some of the stupidest lyrics ever written. To take that piece of drivel and modify the instrumentation to one of the most derogated musical genres is kinda metta - maybe Donna Summers was making a statement of “These people are so stupid, they’ll dance to anything with a beat!”
OTOH while I don’t especially like Waylon Jenning’s cover of MacArthur Park, it’s definitely a different take on a well-known song and deserves to be loved or hated on its own merits.
Yes, but without it we wouldn’t have this masterpiece.
Not sure if you’re aware of the irony here. We had those knock-off compilations of near exact copies of hit songs in the UK; and a prolific performer on these was a young…Elton John. A man, therefore, of many useless covers. There’s even an album of them:
https://en.wikipedia.org/wiki/Chartbusters_Go_Pop/
j
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One of the local DJs would set up two turntables, one with David Lee Roth’s version of “Just a Gigolo/I Ain’t Got Nobody”, the other with Louis Prima’s version. He would play both simultaneously, and switch the radio back and forth between them. It was eerie how they lined up. Not only was Roth singing a karaoke version of the song, but all of the instrumentalists were playing an identical arrangement.
As someone who has a great appreciation for both claymation and Weird Al, THAT WAS FREAKIN’ AWSOME!!!
But wait, it gets wore…or better?
At the time, I knew nothing of Louis Prima, so I thought DLR’s song was OK. I knew it was a cover; didn’t know how note-for-note same it was. I can almost give him a pass because it’s an older song from a different musical genre. Why the %&@# would you cover a song that was maybe only 15 years old and an INSTITUTION IN THE SAME GENRE note-for-note? California Girls to me is the epitome of useless covers.
When I clicked, it said video not available. Try this one
And I have no problem with that one - they changed it up to their style.
In a state of mild dyslexia I once downloaded and album by The Kinx and didn’t realize they weren’t the real Kinks for about a year and a half.
At some point in her career, Joan Jett put out an all-remake album.
Lots of people have done that – Bob Seger, Cat Power and Shawn Colvin come immediately to mind.
A couple of years ago, Pretenders leader Chrissie Hynde even released an album of Dylan covers. Damn good IMO.
Same sort of thing, opposite direction (transatlantic-wise): Rockin’ All Over The World.
The only thing Status Quo did to John Fogerty’s original was to (musically) dumb it down somewhat; so you might argue it isn’t a truly useless cover, because it’s actually worse than useless.But we’re splitting hairs.
Fogerty
Quo
j
And now you’ve given me an earworm I won’t get rid of the whole day. Thanks, @Treppenwitz. 
Ooops - sorry 'bout that!
j
No prob, my favorite car radio station is an oldies station that plays this damned song (the Quo version) at least once a week, so I’m used to it.