I read through this entire thread and I'd like to make a few points. Before I go any further, I'd like to say that I'm a fan of his playing. It may be very simple but that doesn't mean it's always easy. I find "Let There Be Rock" and "Whole Lotta Rosie" to be quite difficult. Very simple beats, but very difficult tempos to keep up that long. At least without resorting to quarter notes on the hats instead of eighth notes, which he doesn't do.
But Phil didn't always play quite that simple in the earlier days. Some have said that it wasn't always Phil on the drums in the early days, but in the video for "Baby Please Don't Go", Phil is on the drums and he's playing a train beat. He plays a shuffle on "Go Down". And the drum parts to "Dirty Deeds" are just a tad tricky. Like others have said, he used a ride cymbal in the early days too.
Why am I bringing all this up? Some have said how his simple parts are about playing for the song. But that may not have been his decision. It might have been the Young brothers that insisted on that. After all, he did get into a physical fight with Malcolm and then left the band. I wonder if it might have had something to do with them insisting on super simple drum parts in more and more songs.
While I haven't heard every ac/dc song, I've heard enough to know that the drum parts got more stripped down in the band's later days. But in all fairness, so did the music. No more shuffles, train beats, or even 6/8 blues beats. Just more and more simple straight 3 chord rock.
All that said, I'm a fan of his playing.