There is not a single thing inside of a casino that is "fun" unless you are susceptible to the dopamine rush of putting something on the line. If you don't find the possibility of losing fun, then you will never find a casino fun, because every game, decision, styling choice, smell, etc is highly optimized around pushing that specific dopamine button and getting you addicted.

Konami, you know, that video game company, makes slot machines. They are not fun because they aren't supposed to be fun to play. They exist only as a legally distinct version of a skinner box.

You definitely gotta play around a bit to find a machine that you like. I personally like machines that I feel like I can manipulate a little (even though that’s probably all in my head) to improve my odds. There is an old school machine that I have figured out a little system with that’s fun to play for that reason, but there are other games that have cool animations and stuff that make them fun to play even if you are losing.