Agassi at his best was the best ballstriker I have seen, including Fed whom I personally consider the GOAT, by the way. When Andre was still young (his long hair and fluorescent spandex 'image is everything' years) he could hit every shot in the book with winners out of nowhere no less outrageous than the ones Fed is known for. But it didn't win him many tournaments so he toned it down a notch going for the extra consistency.
During his most successful years Agassi had perfected his tactics to a point where his game was indeed quite boring to watch- heavy serve intended not to hit an outright winner but to pull the receiver out of position and then take him apart with precision groundies. During this period you always had the feeling that Agassi still had an extra gear which he very seldom used rather preferring to stay in the zone of utmost control. He would still hit the occasional out-of-this-world return when he was himself out of position but he always chose to stay in balance whenever possible and make the opponent run instead.
Needless to say, I much preferred watching the young Andre, that was so much more fun.
On a side note, yes, his volleys always looked a bit awkward compared to the supreme stylists like Edberg and Boris and even Pete but he had excellent hands, good coverage and the luxury of being able to come back behind the best groundstrokes in the game
This helps a lot!