I definitely want reactions RAW. Especially with spells like Shield. What good is having an Abjurer subclass nerfed on hp and no Shield spell. Basically you leave Wizard with only one option, a blaster. That is NOT what a D&D Wizard is designed for. It's the least effective way to play a 5e Wizard. And the most boring. Sorcerers and Warlocks are better blasters anyway.
But with casual players complaining about the length of combat, I seriously doubt we'll see anything close to the 5e reaction system in BG3. Shame
The length of combat wouldn't be an issue if it weren't so boring. This is largely down to enemies taking way too long to make decisions, but getting to make decisions about reactions could help a bit.
Enemies will get faster at making their decisions as Larian has more time to upgrade the AI. The speed at which they think now shouldn't be taken into account when deciding major game design choices.