There's been posts about the relative popularity of BG3's reaction system vs prompts vs other. Searching the BG3 subreddit for "reactions" and selecting the top X threads sorting by Relevance:
Reactions that don't interrupt combat flow - Argues for a QTE-prompt system. Most of the top comments agree with the poster, or suggest permanent instead of QTE prompts. One particular 44-upvote comment says "What's wrong with Solasta popups?" and the top answer to that is "because Paladin Smite" which again, is not a reaction.
Reactions Still the Same - Against auto-reactions. Again, most comments (excluding Paladin's Smite) are in favor of prompts.
Reactions: Meaningful Choices Without Tediousness? - Argues for some type of rework to the reaction system. This one is generally more negative to prompts, with people suggesting other implementations (e.g., presets or "chime in" to tell the system when you want a reaction)
If Bard is playable reactions need to be fixed - Asks for a rework for Bardic reaction abilities if BG3's reaction system stays auto. Top comments agree and/or advocate for prompts, and subcomments advocating for prompts in general have more upvotes.
Reaction system... - Advocates for a more Solasta-like reaction system. Top comments...advocate for a prompt/5e reaction system, but acknowledge some worries people might have.
How I would like to see reactions work - Advocates for a 3-way toggle system: prompt / auto / off. The Best Comment argues against a prompt system, but is also incorrect. You wouldn't have a prompt "every single enemy turn. Every spell cast, every move out of effective range, ..." because characters only get 1 reaction per turn, and many enemy actions wouldn't prompt a reaction. E.g., an enemy moves out of sight and shoves an ally to wake them up.
Am I the only one not too bothered about the reaction system - Post in favor of the auto reaction system. Best comment argues for prompts and the subcomment that argues against prompts gets -10 votes. 2nd Best comment argues for more control. 3rd best comment provides example of when the automatic system screwed them over.
Alternative thoughts on the reaction system and the real system in need of improvement - The OP is against constant prompts and asks why people want the reaction system changed - to match 5e RAW or because it doesn't work in BG3? They don't want too complex of a reaction system. Top-level Comments want more control with counterspell, want more control, and generally are in favor of prompts. In a reply to a top-level comment, OP even concedes that certain things "like smite and counterspell" can agree with having more options.
So it seems like people on the BG3 subreddit are definitely in favor of a prompt reaction system. They are overwhelmingly in favor of some other reaction system than what is in BG3 now.