I don't mean to police what anyone does or doesn't talk about, but respectfully, I don't think anyone is going to change anyone else's mind about this at this point, people are just re-stating the same opinions over and over.
All I will say is that if there never was a fix intended, then some of the stuff in act 3 is one of the handful of things in the game that's just genuinely bad writing (or maybe some stuff being cut that really should not have been). If you truly don't intend for the engine to have a fix, and that was the plan from the beginning, then having a character pretty much tell you "yeah, I invented that thing, and since then I developed a new version that doesn't have the problem that's killing you" and giving the player no option to try and make use of this seemingly incredibly important information is just baffling. If there was never an explanation why the new and improved engines and the knowledge of how to make them can't help Karlach, that's just dumb- I'm guessing I can't be the only one that used saves to go through that conversation like 5 times because it seemed crazy that there's not even an option to bring up that this really seems like a solution to Karlach's engine problem (or at least a big step towards one). If there was an explanation and it got cut- why in the name of sanity would you cut that? It's critical information for explaining why the story goes where it does!
The result is my character comes across as either pretty dim for not realizing the importance of what they're hearing, or shockingly uncaring about trying to help their close friend.
