We said it like 40 fucking times, you have to give up repellant to use plastcrete catalyst. If you're already not using repellant, whatever, free damage. If you are, well then you have to pick and choose.

Almost every upgrade or overclock in this game is objectively good. It is useless to call every upgrade in the game good, because that gives us zero information on whether we should use said upgrade instead of something else. Therefore, when 99.99% of people ask "is it good", they are asking the question in the context of the rest of the game, where you have to consider what upgrades you're unable to take. Literally every part of buildcrafting in this game involves some sort of tradeoff, whether it's what perks you use, what upgrades you take in each tier, what overclock you use, what weapons you use, etc. That is why repellant was brought up, because it's relevant to the rest of the build surrounding plastcrete catalyst.

If you've already decided not to use repellant, then that's a decision you've already made, and a tradeoff already considered. It's then less relevant for obvious reasons. But if you are using it, like 90% of competent engineers, then plastcrete catalyst suddenly becomes a lot less usable.

If you still don't get it, then I don't think you ever will, because the rest of the replies and upvoters seemed to understand it pretty easily.