Registering your trademark makes enforcement easier, but there's a reason both TM and R exist - unregistered trademarks still hold power.

nope, fire your lawyer. you get a common law trademark by trading under a name. no need to register it. TM registration is just to streamline big corps chasing after lots of small abusers in a wackamole way, that’s all. if the abuse in question is as egregious as “I used their product name, barely modified, to market my own thing, which is not just in the same general market but a literal clone of their product” then a judge is not going to say “Ah but I see they didn’t send in a form to register their trademark, so yeah carry on with blatantly stealing their work lol”