Conservation of Complexity

I occasionally step back from projects I'm working on and wonder to myself whether I should reduce the complexity of what I'm doing. It's not so much that any one aspect of it is overly complex... it's just that increasingly, I take for granted a baseline of understanding about lots of disparate technologies.

Write a PHP script? Okay that's no problem. Now it does some database work; you may need to understand some finer points of complex SQL join operations, but that's not a huge deal. Now, some of this stuff is AJAX, but that's no big deal nowadays, right? (Is it still AJAX if it's using JSON?) You know about JSON, right? And jQuery, plus a utility belt full of plugins? And you know about Javascript closures? And the esoteric differences between PHP and Javascript's distinctions between objects and arrays? And some of these requests cross multiple server pools, so you know about mod_rewrite, yeah? and mod_proxy? And about how you can trick PHP into sending extra http headers even if you're just using the stream wrapper for http, and why you'd want to? (And you know what that is, right?) And about cross-domain session handling? And memcached, and the quirks with storing sessions in it?

Any one of these things is no big deal, but all of these things (and probably some that I'm forgetting) are prerequisites to completely understanding a system I'm currently building to let users make lists of their favorite restaurants.

Any coders reading this? Anyone have any thoughts? I don't think that I deliberately complicate things, but what's the appropriate balance between an elegant, comprehensive implementation- and one that a greener developer could unravel in an afternoon?