The exploration feels unrewarding because it's mostly just tiny detours to get a tiny reward that you can see ahead of time, or larger detours to disable an enemy respawn.
The tiny offshoots with a bit of psi just aren't fun and turn exploration into a chore. They're all the same, trivial to get, andd you see what's at the end ahead of time.
Hi, thanks for trying the game!
First of all, I'm sorry to hear you're not finding the exploration rewarding. I get where you're coming from, and an aim for my next game is certainly to have more varied things to find.
Then, a small provocation: If you can see in advance that a given path is just an offshoot leading to more psi, there's nothing forcing you to go there. You can just pursue other paths that you don't yet know where leads. :)
Finally, some thoughts: Many games have a clearly marked "main path" that leads to the current main goal. In such games exploration is optional and leads to optional rewards, or they don't reward exploration and you just find empty dead ends if you try to deviate from the marked path. That's the usual context when talking about whether a game rewards exploration or not.
But in The Cluster, there's no clearly marked paths leading to the main goals (the artefacts). There's various hints, but you still have to explore to find the artefacts. So finding those is the main "reward" of exploration, and simultaneously the main goals of the game. Of course, there have to be other paths that don't lead to the artefacts, or else there wouldn't be any exploration needed. Rather than leaving those empty, there's psi or enemy bases there so that they still serve a purpose. If you will, you can think of those as "consolidation prizes" for having followed a path that did not lead on to an artefact, instead of there just being nothing there.
Still, after creating the algorithm used in this game, I've since learned the importance of using loops rather than dead ends in level design. The Cluster does try to create loops here and there, but there's still a lot dead ends. I'd focus (even) more on loops in future games.