I don't think he's in AEW because he wanted to change the wrestling landscape, or stick it to Vince, but if you asked him he'd say he's proud to work there and he'd also tell you he was proud to work in WWE.
He promoted them on radio shows, podcasts, newspaper interviews and if you think the Rhodes, Fish, Jackson, Suzuki and Omega matches were him phoning it in, he was a cadaver then for a lot of the WWE stuff. He's wrestling on their Youtube shows as a masked mystery man, for Pete's sake. He's busting his damn hump.
He's not into selling merch so the white t-shirt suits his real-life personality. It isn't a knock on AEW; a person doesn't have to walk around in branded gear to be happy with where they are in the moment.
As for why he's in AEW right now, that's because he's seeking freedom to wrestle the way he wants and against who he wants while he still can. Having fewer demands on the commercial side, an enthusiastic locker room, some of his friends from his pre-WWE days and the fun of being part of a new company are other benefits for him in this situation. WWE did well by him, so he has no reason to trash them, but that doesn't mean he isn't enjoying his new role with AEW.
Yes as Bryan loves Wrestling and he gets all the dream matches he always wanted. He comes across a really humble guy in real life so I doubt he’s to bothered about his merch. If he goes back to WWE he get all the royalties from a legend deal.
He gets his dream matches, gets to work a more aggressive style that he likes, and seems to get to do his matches his way as they look different from other people's. I dunno what being proud to work there means, but he seems to enjoy it.
I think he's just happy to be wrestling the way he wants to. I don't think his decision was based on much more than that. AEW told him he could pretty much do whatever he wanted in the ring and he jumped on it.
He just loves wrestling and stepped away from WWE for a change of scenery and to wrestle matches with guys that's he's always wanted. He's just so grateful to WWE and now AEW because he gets to do what he loves.