Hey, thanks for trying the demo, glad you like it. :)
The Oxygen mechanic is not quite where I want it yet and I understand this can hinder the exploration element at times, but I can say this:
It will not be used everywhere, the plan is to use it in select areas and situations.
The "shooting blocks" part is not really going to go away, even for main path progression.
But I get what you mean and I have plans to add more different things you need to do to progress.
The keypad and battery are two examples of this that made it into the demo, but more things will be added.
For the "tedious" part, I've removed some blocks in one area in the demo update I just released, and if I feel like other areas are a bit pointless like this one was, then I'll change those as well in the future.
Anyway, thanks for the feedback. ^^