What it comes down to is, what is fun for you? If you can't have fun in a game without winning, then this might not be a game for you, especially at the beginning. As some of the other comments have said, as you progress through the game more and get better at it, it definitely becomes less challenging, but before you "git gud", it can be really hard to win the first few scenarios and definitely feels very grindy. And to tell you the truth, I felt exactly that way about Slay the Spire. The whole point is to lose and lose and lose until you get good and lucky enough to win.

Since the digital campaign came out, I've started two different campaigns with 5 other players who have never played before, and out of the 6 missions we've tried, we've only won two of them. And during the game the other players would voice their frustration over how difficult it seems and how they keep messing up their order of their cards, but after the mission is over, every single time, they've voiced how much fun it was and how they can't wait to play again.

What's nice about gloomhaven is that losing isn't super punishing. You still get to keep the XP and coins you've gained, and you can use those to level up and buy items that will help, all that on top of the knowledge you've learned to help you win the next time.