Mobley is gonna be an exceptional NBA player if he stays healthy (always a concern with bigs, but do not believe Mobley has an injury history). Definitely will never be as good as Bill Russell, who’s a once in a lifetime legend (alongside Wilt), but he could become a HOFer nonetheless. He’s that good. A comp to Arvydas Sabonis is reasonable (had he played his entire career in the NBA, he would be renowned as one of the top ten, if not top five, centers of all-time).
I would definitely roll the dice with him (he’s virtually guaranteed to be second or first overall) if he could be obtained for Jaylen, especially considering the flexibility we would have with our cap (e.g., enough room to sign Beal and maybe another max in 2023).