Im afraid I have some good news and some bad news about that. The good news is, that it is not related to the polish of the actual game. BG3 looks absolutely crisp on the Steam and GOG version. Sure, it certainly needs some more tinkering with popping in textures etc. but thats more related to driver optimization (not an expert on that, though. So dont quote me on it)
The bad news is that it is a well known issue with Stadia. Specifically with Stadia on PC. This blurriness and the movement pixelation also occurs in many other games on Stadia. It is not connected to your bandwidth. If you have the chance, use Stadia on your TV. For some reason it works well on every other Stadia option than in the Browser on PC. Even worse is, that it could be related to a lot of different issues that - generally speaking - are all solvable. For a little more clarification of the search for the problem, you could read this post:
Chrome Quality IssuesGoogle is aware of this and offers some solutions that are worth trying on their service page. Try the steps that are presented under "Troubleshoot device issues > Computer using Google Chrome". Here is a link that points you in the right direction:
Troubleshooting your Stadia experienceOther than the issues given by Google, there are several others. Here is an example that I found on Forbes. Quite an exotic problem:
Third Time's The Charm: How Google And I Finally Fixed StadiaIf these fixes dont help, I highly suggest using the Stadia+ Extension in Chrome. With this, you can force 4k, change the stream decoding, or simply use and overlay to monitor your connection, FPS etc. It even adds a search bar to the Stadia homepage (weird that Google didnt do this in the first place). Here is a link to Stadia+
Chrome Web Store: Stadia+ ExtensionThere are several more fixes that are out there but I think one of those will fix it for you. If not then be sure to keep me posted on your progress.
Good luck
