@TheCatWithTheHat long term lurker here and I have been in a similar situation but as Miss H.
The guy I was seeing was lovely, I enjoyed his company, we got on really well but I just didn't see it going anywhere. His life was very much tied up around watching and playing Rugby, I enjoyed watching games with him once in a while but couldn't see it happening every weekend. He was a few years older than me and his friends all seemed to be middle aged couples that I felt I didn't have much in common with, again I just couldn't see me socialising with them in the way he did and finally I hated his dress sense! So shallow, but to me I always felt that we didn't look like we belonged together.
We carried on, seeing each on and off, always instigated by him but I went along with it because I liked him. Eventually I just felt I was giving him false hope and said no to the next invite.
I think he was pretty much where you are now and couldn't understand why if we got on well it couldn't progress and I just couldn't bring myself to be brutal and say your lifestyle, friends and dress sense are just too old for me! so I just said I'm not really ready for a full on relationship and didn't want to lead him into believing there could be one.
He's probably a bit put out and scratching his head because I stayed on the apps and through Facebook he will see I'm now in a relationship.
I think you need to accept you haven't done anything wrong and there is nothing you need to change, you just weren't right for her. She likes you and because of that is trying to let you down gently, but her ambiguity is allowing you to believe there still may be hope.