Here is my problem with your way of thinking: I play with a group at a local nerd store where most of the group doesn't talk much outside of the gaming table. When we get together it works best if we can all play off what is in the books. Telling everyone that you are running something for 4e next week tells them they should expect to play by the book. If you want to communicate to them that you intend to change things a little bit means, at least with this current editions, that you have to really spell things out very clearly. The chances are small, yet it always seems to happen, that when you change something tiny (for the sake of this argument lets say adding more wonder) you affect the entire game. When you decide to make things less explicit (which is how the book lays them out) there will inevitably be a character built around monster knowledge, or an artificer built around magic item manipulation.
In this situation it becomes very easy to 1. screw your players out of the character they want to play because your flavor changes the rules that governs the character they want to play or 2. you have to spend a lot of time specifically writing out how your flavor changes affect this or that aspect of the game. Everyone should be able to approach the game being confident that what they read in the book is what they will see at the table, so they can build their character accordingly. If a system is so intricate that a specific character can be ruined by a tweak in the flavor of it's rules (which ends up affecting those rules), then the system could use some work in my opinion. You shouldn't have to worry about walking into a game with a character that just doesn't work even though it was made by the book purely because the DM changed a little bit of the flavor of the game.
The point I'm trying to make here is that 5e could be designed from the ground up in such a way that making a small change in flavor wouldn't have potentially devastating or far reaching effects on the rest of the rules, like it does now.
I'm sorry, but I find this argument to be preposterous. It might have been almost a decent argument WRT to 3.x where the mechanics of things were explicitly tied to the fluff. 4e was the answer
to that. If you missed that message somehow I think maybe you want to go back and actually look at how 4e works and maybe it will start to make sense.
And the whole concept that somehow a game would be ruined if anything was varied in the slightest degree from book standard? Huh? How could you have even played 2e? We aren't talking about major modifications (or even ANY modifications) to the core mechanics of the game, the mechanics of classes, etc. All we're talking about here is ordinary reskinning of things and garden variety homebrew content like a new item, ritual, power, maybe a new race. Its expected that people will design new monsters, change existing ones slightly, etc.
The sense of wonder and imagination did not come from any rulebook and has nothing to do with the rules. I've been running D&D games for 30+ years, and the majority of that time with a lot of the same players. They have always known every single rulebook, supplement, etc cold. Any group of "game nerds" as you describe it would certainly be the same. You aren't going to suprise them with any monster that's in the book, or magic item, or spell, etc.
How you're going to capture wonder and imagination is in how you put the elements together and how you describe it. At best all a rule book can do is give you suggestions and guidelines on how to do it in a workable fashion. 4e does that better than any previous edition of D&D as far as I can tell. And its a good solid system, so if you add in a new thing or modify an existing thing, the mechanics of the game are there to deal with it.
The game could still be improved in my opinion, but going back to a poorly written set of mechanics in the misbegotten notion that it somehow adds a sense of wonder to the game is just nonsensical. It will do no such thing. If you've lost your sense of wonder in the game, I have to suggest you may need to go look for inspiration outside the rule books. Heck even within the various 4e books there are a lot of story ideas, background info, and settings you can draw from.