I've been trying very hard to like 5e because I want to introduce a young relative to the game without the inconvenience of tracking down OOP books. Using the current edition would be easiest...but I've resigned myself to viewing 5e as an alternate prime material plane (0, 2, 0).
(Gloriously Gonzo
Mystara: 0, 0, 0;
d20 Modern: 5, -4, 5) ...
THE WISHLIST
A dedicated
Campaign Setting / World,
that is optimized to show the ruleset at its very best. What cool / fun things can you do with this ruleset? New options? Old options adapted to the new environment? This is a carrot that can offset ruleset changes (stick).
As a bonus, reserve some landscape for customization (beloved homebrews, importing nations from other settings, Gazetteers, etc...)
Optimize the print version for tabletop play.
I like the
Advantage / Disadvantage mechanic in 5e, it's elegant, so I think that should stay.
Alignment is a useful
toolset.
A convenient shorthand that provides in game guidance when role-playing a character.
In my opinion, it is also a subtly subversive way of making people think.
The "discussions" about it that occur "out of game", to me, are a feature, not a bug.
(Pre-emptive disclaimer: if the
only tool you have is a hammer...yes indeed, everything starts looking like a nail.)
Allegiances: an elegant adjunct to Alignment. The distinction between the two is food for thought.
Four or five
Core Classes, followed by their derivitives. State which class(es) the derivitive comes from, even if it's only on a chart somewhere in an appendix. (Nothing wrong with Gestalt goodness

)
Sincere Question Asked in Ignorance: In 5e, is it even possible to play a 3e style wizard without being shoved into a specialist "sub-class"?
Attribute / Ability Scores: yes.
Levels: yes, but stop dancing around level limits.
State what levels a book covers, but do not state a level cap. (PHB's + Epic Level Handbooks...I'm looking at you.)
Core Species / Additional Species: What are the core species in this edition? Any new ones to play with go into the Core Species for this edition (PS 2e introduced Tiefling & Aasimar, IIRC).
Additional species: valid to play (with suggested regional backgrounds?).
Some
Sub-systems Tied to Feats: if the DM allows a feat, the attached sub-system is operating in
this game.
Leadership / Sidekick etc. = Hirelings / Followers / Henchmen / etc...
Holding = Guilds / Strongholds/ (Bastions?) / Dominions etc...
(Psionic / Arcane / Divine) Abilities = "Spellcaster" classes...
Playing the game is a journey.
(But what is the system endgame goal? Rulership? Immortality? System Mastery?)