In my opinion, at this point in your life, you don't need to write off alcohol entirely until you've spent time away from it. Unless you're
pathologically alcoholic, alcohol in itself isn't a bad thing.
Try occasionally taking time off from it. Have a week where you don't drink at all, then allow yourself to drink moderately, and repeat. Perhaps you can go even longer than a week. That way life without alcohol stays familiar.
In terms of fun without it, if you think you can't have fun without alcohol, that may mean you just don't know what's fun for you yet. Try participating in different activities, including things you think you won't like, and maybe you'll stumble across something you'll enjoy.
I think one's relationship with alcohol is much healthier when there's an alternative source of pleasure.
Oh yeah, and as others here have stated, find a different friend group to branch off to. It's not that you need to completely abandon your current friends, but our social groups really determine a lot in how we feel and behave because we all have a need to blend in and be a part of one. Maybe you can have you "alcohol friends", and then your friends for other things. If there can be some overlap there then great, but if your goal is to have fun without alcohol then you need to be around others on the same page as you.
Lots of people enjoy sports (watching and playing), video games, hiking, puzzles, board games, and movies without alcohol or at least alcoholism. It's possible to find others to do those things with over the internet, but don't let yourself think there's nobody to do them with IRL, as hard as that can be right now.