Having an active reaction system like Solasta will slow down the game quite a lot.
Is demonstrably false, and has been demonstrated and shown to be so multiple times. This is a fiction. It's not true or accurate.
without making this a pure tactic simulator with hour long combats thanks to pop up menus every three seconds.
Is ridiculous hyperbole that only serves to make your other comments look dishonest and disingenuous.
Everything else has already been suggested and chewed over in the course of this thread, multiple times.
A system that can be set up in your options to prompt the player when reactions are available, and can be set to always take certain ones, or to never take other ones, or to remain as hands-off as it is now if that's what is wanted, seems to be generally agreed to be the best way to satisfy everyone's wants and needs, which is what we should be aiming to do.