Having recently played Solasta for the first time, I've got to say their reaction implementation works flawlessy and doesn't interfere with the flow of combat at all in my experience. I truly hope Larian will make some real considerations on how to properly implement reactions. Whether my mage uses his reaction to attack a fleeing monster, or saves it for a potential shield cast later, has a very big impact. This is something that is highly unlikely to be fixable with mods, and needs proper support from the game itself.
i must really say.. i'm growing on solasta. bear in mind i honestly just completed bg3 EA for only once (since the launch) and really don't have much motivation in starting at all seeing what larian is really focusing are just cinematics and visuals. i was really surprised, solasta implementation of the dnd5e is close to flawless for me (however i read that they nerf the darkvision as due to that human is really on the losing end). i must say i truly didn't pick human at all.
reactions in solasta is really a game changer. not to mentioned the implementation of half-cover, 3 quarter and full cover. bear in mind.. before playing solasta.. i know NOTHING about dnd5e. and that game teaches me the rules.. i'm speechless.