One thing occurs to me that I don't think has been done in any previous edition, but that recently increasingly jars on me:
- There is a 'default game world' hard-coded into the initial rules set.
D&D is not Gurps or D20. D20, for example, is a set of rules mechanics meant to be adapted to whatever genre and setting you like: Superheroes, 007 spies, steampunk, eldritch horror, Star Wars, etc.
D&D is first and foremost pseudo-medieval dungeon looting and monster bashing. Whatever you ACTUALLY do with it is your own business and we should all have fun, but DO NOT strip D&D of the very genre elements for which it should be EXPLICITLY intended.
I wouldn't expect everyone to embrace with sloppy kisses the implied setting that any particular edition might present, but I emphatically believe it NEEDS to be there. Change it if you like (and in fact, if you're DMing and you never change it you might want to question how good you are at your job) but newbs should be able to pick up the core books and
without having to buy a seperate game setting to provide additional details, and without having to make up those details themselve without knowing what details will be needed/wanted short of taking an online training course be able to get something like a basic game up and running.
Once an edition is published there will be YEARS of time for WotC and/or others to invent, adapt, and publish specific game settings that will make whatever changes to religion, magic, races, classes and even core mechanics. DON'T turn D&D into a bland,
lifeless game by bleeding it of the things that give it any REAL flavor out of the box.
JMO.