Yes, that's true, you could do that. It's likely your solo guild would come in dead last and win very few crowns though... which means it would take forever to level up your buildings, so you will be progressing at a very slow rate and maybe getting enough Merits for 1 gladiator pack every 5-10 days. So I suppose I wouldn't view that as being any different from a low-level bot that just grinds ranked matches all day long. And remember you still have to pay DEC to make the guild and at least get a level 1 Store & Arena, so there is an entry cost associated with doing this.