Unheard of actors is generally a good thing when doing a new series: there isn't really a series where it's felt like a good thing that it was being initially run as "starring <well known actor>". If they're any good at all (and most actors are absolutely fine) then they'll be good.

The CGI on the other hand I agree though I can put my finger on exactly the issue: the virtual sets "feel" small in the footage I've seen. There's a certainly quality to the limitations of CGI which generally constrains the camera because you can't actually pull out far enough to make it feel large (I suspect getting the lighting to cast onto the actors right is also a subtle challenge here).