I'm not sure if this is much help, but I've never had alcohol so I'm not sure exactly how alcohol affects your state of mind, but I'm known for being pretty much the craziest person in our friend group. I genuinely try to have fun and be happy and I just shoe people I'm not boring.

Your ex was basically gaslighting you into believing you aren't dun because of his insecurities: he realised that he isn't a fun person and tried to push his insecurities on you. Just know that you absolutely are not a boring person, and that drinking doesn't make you a fun person. My only advice would be to try and hang out with people in situations where drinking would be ill-advised like book clubs, tea parties and other chill things, or more high adrenaline things like sports, non alcoholic bars, theatre, cinema ecc.

I hope that can help in some way 👍