Nah his offensive game is brilliant. He's a top-5 defenceman in the NHL at driving offense at 5 on 5. He just doesn't score a lot on PP, largely due to not getting too many opportunities with the top unit.
In a world where guys like Jones, Werenski and Nurse are making 9.5 million dollars it's little silly to say that McAvoy doesn't deserve at least 10. If he used those three as his comparables he should be starting his negotiations with 12 million.
Brilliant is a stretch. McAvoy's 16 5v5 points in 2021 put him equal 30th in the league, and well behind Jakob Chychrun's lead-leading 26. He wasn't even the top Bruin, being beaten by admittedly late-entry Reilly, and Gryz's PPG was also better. The guys putting up the really high even strength numbers are otherwise largely who you'd expect - Carlson, Weegar, Theodore, Nurse, Chabot, Martinez, Barrie and Letang. 2020 was better - Chucky was equal 7th and his 26 5v5 points put him pretty much on a par with the other top guys except Josi, Carlson, Ekblad and Makar.
Add that to the eye test and the unquantifiables, and I think it's safe to say that McAvoy is very good in terms of his offensive playmaking and passing abilities. But I think there's a distinction between very good and brilliant or elite. There's a level that a handful of those other guys are on that Charlie can't reach, and when you also factor in his weak shot, IMO his all-round offensive game comes up a bit short of the very best. And I've never really bought the argument that if only he had more PP time then he'd shine on it. For sure he'd bank a few more points, but he's not really a threat from the point and his passing is decent, but he's not Krug. Clearly Cassidy doesn't overly rate his abilities in this area either, so I don't think I'm going out on a limb with that assessment.
Exactly how much that impacts on McAvoy's value is debatable. To me Nurse, Werenski and Jones are all slightly better offensively than him - Nurse pretty much in all areas, Werenski and Jones because they are superior shooters and PP performers, although their even strength play is really no better and Jones seems to have declined of late. But then Charlie is at least as good defensively as all of them, even allowing that there are still a couple of deficiencies in that aspect of his game that he can continue to work on. So if those guys can all hit the 9s, as can a superior offensive but inferior defensive player in Hamilton, then I'd say that's the benchmark right there, and at the very least McAvoy's going to come in just under that. So I'd say below 8.5 is a steal, 8.5 to 10 is just fine, above 10-10.5 I start to get edgy and consider my options.