That you think LLMs are the cure to loneliness misses what a "cure" even looks like here. OP clearly writes well enough to get first dates - the issue isn't conversational content but likely body language, energy, presence, the thousand micro-signals that happen below conscious awareness. You can't chatbot your way into better posture or more relaxed eye contact.
This is classic LLM wrapper syndrome. Someone has a hammer (conversational AI) so every problem looks like a nail (conversation optimization). But the actual failure mode here probably happens in the first thirty seconds of meeting, before anyone's even said anything substantive.
Op would probably benefit more from something social like improv classes (physical presence, spontaneity), dance lessons (body awareness, comfort with proximity), or honestly just hanging out in social spaces doing things they actually enjoy rather than performing "date behaviors." The energy of someone genuinely engaged in something they love is magnetic in ways that no amount of conversation optimization can replicate.
I just don't believe that "practice talking to a computer" will ever be a sufficient platform to teach people how to be genuinely charming, let alone charmingly genuine.