It's definitely the norm.
He was good for what he was when he was younger, but yeah.
I remember thinking he was the best technical player of all time when I was a kid, I laugh at it now.
That said, just being able to play well isn't the most important thing, it's the music you write. There are tons of players out there that could absolutely blow him out of the water in terms of skill, guys with YouTube pages, professional musicians, I could rattle of a couple dozen better players, but they've never written for or been in one of the biggest bands in the world.
It is what it is, he doesn't have a whole lot of skill, but he can write some tasty solos and riffs.
Another funny thing, Mustaine was replaced by him, he's another guy that, while he's a great composer, when it comes to playing/singing, he's atrocious.
Sometimes the best composer can barely play a damn note or are over-rated, but being able to play and being able to write, they're two different things. You can hire a guy to just play, that takes skill/talent, hardwork, dedication and not everyone can do it, especially live. But writing great music I think can be even rarer.