It’s likely that you’ve seen movies which are mostly (or entirely) ADR dialogue - so unless you were incredibly distracted by it.

It’s important to note that the recording surrounding being entirely quiet and “flat” is what sound engineers need to make the “building blocks” that they work with when creating bombastic film soundscapes. Sound engineers add things like echo, and reverb, and placement, and environmental noise to every line of dialogue in the film, and having a “neutral” starting point makes their job easier. As to actors / emotion / chemistry… that’s why actors are good actors.

An actor who can’t do a convincing ADR take will find it difficult to get work.

Being excellent at ADR is one of the “unseen” skills that’s incredibly important to become a top-level actor but that audiences don’t generally think about (things like being able to maintain emotional continuity in a scene that might be filmed over the course of several weeks, and at radically different times of the day, and often when everyone involved is exhausted).

Actors who aren’t good at that type of “invisible” work that no one thinks about, don’t tend to even get cast in the first place.