He had a phenomenal 2018 season. A season that outside of winning a major - was always going to be incredibly difficult to replicate. He's the epitome of "streaky" by virtue of his intrinsic, mechanical nature. When he's good, he's really good. When he's not really good, he's playing two tournaments in the same week... making the cut, then trying to finish higher than he expected. We could make the same argument about DJ, Rose, Spieth, whoever... the difference is they've played in enough majors to be comfortable enough to figure out how to win one.
Bryson has only 10 starts in the majors. I'd rather see him struggle early on in the majors and have to learn how to get his game in shape leading up to a major than be like Keegan Bradley, for example, who won the very first major he qualified for, only to then basically go half a dozen years without even a single regular tour event win.
His tedious nature aside, he's still got plenty of time to learn. And plenty of time to win. And plenty of time how to figure out how to throw away a lead in a major on Sunday and learn from it, or allow it to define him as a player in the biggest events.
Three years ago had you wagered me that Koepka would win four majors in the upcoming two seasons, I would've called you a lunatic. It's much too early to assume anything about Bryson imo, other than he's sometimes a slowpoke and he's an eccentric.