You see, in my game at least, the 5 skeles were in a tunnel. You could not jump above them. There was a tiny alcove where you could go up before it hit a pool of water, but there was no room to do as you describe.
It's always the same map -- I hand crafted all those. I'm not sure which one you're referring to, but perhaps it was the one where there's that long narrow deathtrap behind a red slime? The one with the green crystals and the workbench? The red slime protects you from the skelebots unless you kill it, and there's no concrete reason to definitely kill it (the stuff you want is on the other side of the pond). In that case, yes, there is no way to jump over the heads of the skelebots where they are. But there, either one of two things happens:
1. They chase you and you lead them to the edge of the water, where you jump up on wood platforms you've pre-placed or that you place as you run (or you scamper up the ladder to the tunnel above that one). There's no reason to stay in the tunnel to fight them without fleeing; you don't have room to maneuver, so to not tactically retreat is suicide without better gear.
2. Alternatively they don't chase you, and you fire on them from range and kill them before they get you.
Again, something it's trying to get you to experiment around with. There is room in every chunk somewhere for you to dispatch all the skelebots without having to take any damage; there is no room anywhere in there that is short all the way through. It's trying to get you to experiment with the tactics of drawing dangerous foes out into parts of the chunk where you can dispatch them more easily, and using the terrain to your advantage, rather than letting them use the terrain to their advantage.
I was presuming you meant the earlier rooms when you first meet the skelebots, where the natural tendency is to jump down into the skelebots and get murdered the first time; then the second time they are more cautious and need to put the wooden platforms. Then finally you reach that room where there's no space for wooden platforms right where the skelebots are, but there's loads of room right where you just came walking from (and even some handy water the skelebots can't cross).
Again, I'm not trying to slap you around for not instantly seeing all the intricacies of using terrain or similar; it can be nonobvious, and playing on a higher difficulty means that if you don't figure it out right in your first encounter or two, you probably die. And I've no doubt you'd have seen all that really soon without my mentioning it. But there's actually quite a bit
more tactics to the constrained spaces, I feel like, because there is more risk and you have to draw your enemy out. Of course, there's some good tactics to all of it and it really varies in style; so what works outside doesn't tend to work indoors, and what works indoors often doesn't work quite the same underground.
Fighting in each of those three areas has a distinctly different feel to it, but at no point are you expected to be a fast-clicker that just whales away on enemies that are whaling away on you, at any rate. Hope that helps!