Why does English dubbed media sound like the way they do?

Most media has an "M&E" version, Music & Effects.

In the course of sound editing, everything possible is split apart:

Spoken dialogue gets its own set of tracks.

"Good" noises caught on-set (usable footsteps, paper shuffling, etc) are called Production Effects (PFX), and those get their own tracks. The dialogue editor has to dig those out of the dialogue tracks and separate them into their own tracks. The dialogue editor also cleans out any "bad" noises.

Foley, like footsteps or horse hooves, get its own set of tracks.

Voiceover (ADR) gets its own tracks.

"Futz" meaning stuff that's coming through a speakerphone or something, gets its own tracks. That's all created in post production from either ADR sessions, or wild takes on-set.

"Hard effects" like explosions or other things that the post production team create, or otherwise pull in from outside of what was shot on-set get their own tracks.

Background sounds get their own tracks.

Music obviously gets its own tracks.

The M&E mix for international re-recording is generally the following:

PFX Foley Hard FX Backgrounds Music

That way whatever team is overdubbing the foreign language tracks can work with material that doesn't interfere with what they're trying to do.

Part of the "uncanny valley" effect that you're getting is that international overdubs have to be done in a sound booth, and then reverb/delay has to be added to make the dialogue sound like it's actually being spoken in the environment you see onscreen. Faking that experience through reverb and sound design is actually a really, REALLY difficult thing to pull off convincingly. There's just no substitute for all the tiny cues our ears perceive from the nuances of what's actually recorded on-set.

That's why it so often sounds fake. Because it is. And like Mr. Plinkett says, your ears might not have been able to tell that something was wrong, but your brain could.