And yet Mark Ruffalo is only 5’8”, not exactly bulked, and he did a convincing job playing an 8’2” character.
TV budget, folks. They could just use the existing high end model from the movies for Hulk, She Hulk has to be created from scratch. Has there been any other similar shows with a large shapeshiftiing character? What effects did they use? And how did it look?

If your benchmark is Hobbiton, that won't be met, because this production is nowhere near that scale. And the automatic assumption that practical = better is very suspect.