It's not actually easier to customize D&D to do what you want, unless you're staying in a pretty narrow band of play. People spend huge amounts of effort to customize it because that's what they know and there's a weird identity thing in saying you play D&D, even if a heavily house-ruled version. Most of the effort I see people doing in trying to modify D&D would be clearly better served by picking up a game that already does that. What's even more odd about D&D fixation is the edition thing -- people stick to an edition. You'd think, given the huge range of OSR games that have already made modification to do specific things they'd be more used, but people really seem to want to put a designer hat on with D&D. Further to that, having only had experience with D&D, they rarely actually realize what the game is doing because that's all they know, so their mods don't really address the problems they have. There's a reason that a personalized version of D&D is usually called a Fantasy Heartbreaker.
I wish every D&D player would, at some point, give an earnest try of a different system. They can hate it, that's fine, but the experience is still very rewarding when you come back to D&D-- open eyes make for better choices. My D&D games got lots better after I branched out because, when I play D&D, I'm not trying to make the game anything other than what it is; I embrace it and play it that way. It's when you use D&D to do something that D&D isn't that you get into trouble, and most with only D&D experience think D&D can do way more than it actually does.