How is soy sauce not vegan? There’s only soybeans, wheat, water, and salt in it.
Anyway, tofu is pretty good and may be better than chicken in some recipes. I recommend buying the good stuff (fresh tofu from any Asian grocery store should do, don’t buy western discounter brands). Maangchi has great recipes, this home style tofu is great too. Easy as well.
How do you season it? In my experience, ground beef/pork has no substitute that gets even close.