Playing for Boston this year (and being injured during the season) also doesn't help him. People saw how Terry Rozier, Jaylen Brown, and Jayson Tatum did without him on the court, and I'm sure people started to wonder if Kyrie's impact isn't as outsized as we used to think. It's a similar thought to how people used to think about some of the Spurs from ten years ago.
His greatest skill (one-on-one scoring/creating) is something that doesn't strongly affect his teammates, outside of some gravity impact.
In a way, one-on-one scoring/creating is such an interesting topic, because it's the ultimate fall-back when everything else fails (defensive schemes, cold teammates etc). A player who can do this at an elite level will
always have value, as it's one of the few skills that have value as a standalone attribute, and is not dependent on anyone else.
But it's also far more isolated than other skills in terms of impact on others. A great team like Boston has a strong winning foundation (team D, various scorers/shooters, etc), and doesn't always need Kyrie's one-on-one ability on a nightly basis to win games.
That said, there's a reason Kyrie becomes more and more valuable the deeper you go into the playoffs -- because he has the ultimate fall-back skill when shit starts to go wrong (as it inevitably does in the late playoffs). Come Finals/CF time, you could have one of your key young guys freezing up (see: KAT last year), some of your role players losing their legs and going cold (see: Houston G7 WCF), guys abandoning sets and forgetting what got them there (see: Toronto last year), and/or your other key guys battling injuries (see: top teams every year).
So in a way, Kyrie should be both overrated and underrated, as he is.