So is there a way to do homebrews right in your opinion, or should everyone leave it entirely up to professional designers?In my experience, homebrew worlds are a mastubatory exercise in PC railroading. Most are an excuse for some schmuck DM to impose his personal aesthetics on players, while hiding behind the smoke screen of "Sorry...Paladins don't fit my world" Those that aren't have probably been published. I just don't see any good reason to wile away the hours working on a custom setting while there are a number of pre-established and ready made campaigns on the shelves already, unless you plan to railroad the game to oblivion.
Dungeons & Dragons is supposed to be a game, one that is played for fun. When a DM prioritizes artistic expression over fun in a game, then they are not doing their job....furthermore, going to a game expecting D&D and getting "Sit Down and Let Me Read From My Newest Fantasy Masterpiece" instead is an immediate joykill for me. If an epic story that is under your exclusive control is what you want out of your game, then you should be writing a novel instead...D&D is supposed to be a collaborative effort.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.