It's extremely difficult to write a great melody, much less produce a great song. While I don't often listen to his tracks for "fun", I have to give him that he's a great songwriter.
Very few people can come up with catchy tune on consistent basis.
He reminds me of a prolific young Japanese orchestra-style music composer Sawano Hiroyuki who has written some terrific soundtrack for TV, though I'd consider him many level above Max Martin.
Same with Diane Warren.