The dude has a writing credit for the song, and is getting nice fat checks every year from it... so I’m not sure where he is coming from claiming she says she wrote it solo.
Has she taken more credit for it than she deserves? Probably... they are the ones who get the interviews, not the songwriters... so I am sure she’s exaggerated or embellished the story of the songs creation to “play to the crowd” over the years. Let’s face it, at the end of the day, she’s an entertainer, that’s what they do, entertain.
Also a pop artist not having a deep understanding of music or musical theory? Those are a dime of dozen, and have been for decades.
Yep, bad form on his part to dish like that. Songwriting can be a sausage factory whose doors are better left shut.
She is the one who made it a hit not the writer.