I think a tasteful combination of reward and pointless is okay too. Main idea is Dark Souls. Not every single hidden path leads you somewhere, but the reward for trying is usually worth it. I think the snub on some keeps the times where you do find the secret to be that much more exciting.
If you get a treat every single time you try something, each one feels less big.
That being said, having to go on a stupid complex exploratory venture to find a piece of garbage just sucks lol. Best example I can think of is Zelda Twilight Princess. There are some amazing and complex (for Zelda) challenges and puzzles that feel amazing to complete and then you find the chest and it’s a fucking stamp that has no effect on the game at all and is just a huge disappointment.
I think improving the AI/capability of the enemies is a somewhat reasonable way to manage difficulty, but I hate the method of just giving enemies more hp or reducing damage in most cases. It’s not a skill difference at that point, it’s purely endurance. For example, in the first of the newer God of War games, increasing difficulty didn’t make the battles much more interesting, it just made them drag on, so you’re just doing the same sequence over and over with little to no variability. Looking at you giants with the pillar.