Early in the game, the bosses are sort of like puzzles and everything else is easy to kill without trying. When you get deep though, that is by far no longer the case. You have to put together a well thought out team in order to win, and even then there are going to be things too difficult. The nice thing about Siralim 2 v Siralim 1 is there are now many MANY options for what that team could be. All teams have a few things that will beat them (by design) but there are many that work well. The fun is getting a team you like, with materials you have to work with.
There is some power balance lost when you go back to siralim, but it’s not THAT huge. It is 5% to go to the next realm, and free to go back to siralim + 15% to go back to realms from siralim. So you are only seeing a 10% loss, which can be as few as 2 battles to get back. If you are complaining that breeding is not available yet, it sounds like you will be going back into town with some regularity to do breeding anyways soon. Breeding gets unlocked after one of the early boss battles. I was a bit sad I couldn’t breed as soon as I started the game, but I just played for a little and it was unlocked quickly.
I did not feel like it was much of a “tutorial” at all. It was more of a storyline to give some direction if you are lost, and it added some flavor early on. The boss battles actually made me think about how to make a better team, which was then very helpful when I started going deeper. If any boss gives people trouble, you can overlevel yourself and it makes them easier.
I honestly feel like you really didn’t give the game much of a chance. It has bosses every 5 floors or so (even after the story is over it has them in nether realms.) The enemies get harder and you have to pay attention to your team more later. If you want the game to be harder, make a good team and blow through the easy stuff. It sort of needs to be easy in the beginning so people can get cores and materials to actually make a better team before it gets impossible to play.
As far as Steam goes, I don’t think it’s normal to get a refund on a game you played. You apparently didn’t know what the game was when you bought it, which is no one’s fault but your own. The reason Steam has a “hide” option is some people get batches of games from humble bundle and might not like some of them.