Why don't I run (or like) Eberron?
Warforged. PC-playable quasi-constructs without the drawbacks inherent to all other constructs (e.g. constructs can't usually be cured, Warforged can). No thanks.
The cosmology...or lack thereof. Rather than Eberron's distant aloof deep-background deities I want in-your-face Greek or Norse types that sometimes willingly meddle in mortal affairs and that take a direct interest in what's going on; and I want Clerics to be the mortal agents of said deities.
The technology. Had they fully leaned into gunpowder-less Victorian-era steampunk I'd be much more keen, but the art-deco post-WW-I tech - and aesthetic - does nothing for me.
All that said, one thing Eberron does do well - and that really should be ported to all mid-to-high magic settings - is the magic-for-the-masses piece. I mean, for example it just makes too much bloody sense that city streets in Greyhawk or the Forgotten Realms would have Continual Light streetlights, etc.