I don't know what expectations you'd have for Barron, but personally I don't see any issue with his performance given he's one of the youngest D-men who has played regular minutes in the NHL, the team he's on and the role he plays. If he was "knocking it out of the park right now", it would be a league-wide story.
OP listed RD that: is actually rumoured to actually be available now (or at least from now to next seasons TDL (Savard), a more veteran depth guy that has been healthy scratched more than Barron (Kovacevic), a guy who has played only a few games at RD this season (Guhle) and two D prospects that are a ways away from making the NHL (Mailloux, Reinbacher).
The reasonable interpretation of the OP is that Montreal has a lot of RD, they think Montreal would move Barron if in a trade (which they explicitly said wouldn't necessarily be one for one) for x, y or z caliber prospect/young guys. Not Montreal has a lot of RD, would they waive Barron next season and they're trying to get something for him now. Whatever you think of the validity of that appraisal is up to you, but the waiver thing is out of left field.
Plus, Montreal's carried 3 goalies the entire season because they don't want to lose Cayden Primeau on waivers and have reportedly be willing to do that for not just this season, but next as well. Of course they're not going to waive one of the, like, 13 D-men under the age of 23 who have played 50+ NHL games already.