Thank you for the comment!
Reactors and Spires are intended to be one of the main ways to gain "prestige" points, which is why they might feel useless in the demo...
The Demo is designed to be played actively, since there is no offline-progress; which is why you might feel OP after leaving the game open for 8 hours. Although, thanks for sharing your thoughts on the balance!
As for the Disposable Biocells, I kinda forgot to add a number% display in the tooltip, will fix that in the full game!
Again, thanks for writing the comment and taking so much of your time to play the game, really appreciate it!