Hello.
I never thought about it being fun. When I was a kiddo it was fun, until adolescence, then it wasn’t, then it became a real drag, and then I think I fell into bad habits of sin…
Since 2006, when I had some profound spiritual experiences and began to rediscover my faith, yes, I think I can now say that going to church is fun. I like to dress up for church, so I get to pick out an outfit, and that is fun. I always get to go to confession before Mass, and I race up to that. It’s like when St. Therese of the little flower said it’s like jumping into God’s lap. So, I get to dress up and then jump into God’s lap. Then, I see everybody else in the family, all sorts of ages, shapes, and sizes, and that’s just great too. God has a very good sense of humor. Then they tell us truth (well, hopefully they do), there’s nothing like an unadulterated truth, and we get to sing it, too. Then we get to eat supper, and sing about it some more, then they tell us to tell others about the Catholic faith, so they can experience the joy. Then we all get to laugh and eat doughnuts if we want.
In these ways I think going to church can be fun. I don’t mean to minimize the seriousness of the 4 last things however, and that we are meant for heaven and not this world, but only to answer the question the OP stated.