In my case I felt like my other therapists could never understand me on a deep level because they were too "normal". Once I found a therapist who was a huge nerd and understood how my identity as a nerd shaped my life, everything clicked into place. (Bear in mind that I grew up in a time when being a nerd was considered a bad thing). He also specializes in LGBTQ+ care so he was able to understand my transition easily.
Basically it just makes sense for me when he asks "How did that make you feel?" And I can respond with "Like rolling a 1 on an easy DC check." and he gets it.
Sounds like you're doing everything you should do just by being there for him and lending an ear. You cannot be responsible for dragging the man to happiness and supporting him on your own - We each have a responsibility to do that ourselves. I think the bigger question is whether you can be happy with your boyfriend if this is just who he is. There's no right or wrong answer to that.