What makes Gregorius interesting is he's gone from the fringe to possible major leaguer. You might be right that AAAA is his ceiling, but what if he's a modern Pokey? Pokey had a career. Still the best defensive 2B I've ever seen. A guy like that has his uses.
Interesting is inherently subjective. Hamilton setting the all-time single-season SB is pretty interesting. Stephenson's blue chip arm is pretty interesting. Cingrani's dominance is pretty interesting. Jesse Winker's pretty damn fascinating too.