After 7+ years of DMing for 5E, I'd say D&D hasn't spoiled me on other systems at all. I've read through a lot of rule systems (Cortex Prime - Marvel Heroic RPG and Tales of Xadia in particular -, Vampire 20 and Mage 20, Continuum, PbtA games like Masks, and even other D&D offshoots like 2E, OSE and Pathfinder 1E/2E) and I would prefer running them if that system will fit the kind of story I want to create. But I have to admit that I feel the most comfortable with 5E. But I'm definitely seeing the limitations of the system, and I wouldn't hesitate abandoning it when it doesn't serve me.
As a player, it's not that I'm spoiled by 5E, but it's that I can't find anything else. Everyone around me runs 5E, and try as I might to show interesting other systems to friends, they seem to stay with 5E no matter what they're trying to do.