As I've said his minor league profile is quite impressive. He's hit and hit consistently at every level. His scouting profile also describes him as a plus hitter with average power. He's been pretty consistently a 130 wRC+ player his entire minor league career including 144 this season. Not all players can make the jump, but if that can ever transition to the bigs with average defence (OF is a pretty easy position to teach) he could become a t 2-3 WAR player for a few years.
You said he's below replacement level so far, that isnt true. This season in a small sample size yes, however for his short career he is above replacement level.
Nobody is expecting him to break out in a big way and be an all-star, but for him to contribute and be a solid piece for the next 3-5 years is not unreasonable what so ever.