He's our 4th best. Barzagli and Benatia (earlier in the season when he was awful) were repeatedly preferred. If he's not better than early season Benatia or current Barzagli he should be sold like Ogbonna, and be replaced with somebody better.
tbf that's what Beppe tried to do with Howedes, and Caldara for next season. It's too late for this season now.
Barza has generally played in a back 3 or as RB this year. Rugani has played more minutes as a CB. Allegri chose experience for this CL match against Madrid and it backfired. You are exaggerating how little he plays imo, and also about the quality of opponent he has played against, I listed multiple matches against upper table sides he played in.
He's a good young player with lots of potential, especially considering CBs often play at a high level into their mid-30s, and I highly doubt we sell him. ~2000 minutes of match time this season isn't going to stunt his development.
That being said, next season is a vital one for him.