I think the issue s many people dont get is that there are multiple way to handle design. TSR, WOTC, and D&D have chosen different ways to handle the fighter and every other class in the 5 editions. Someone might agree with one editions's design for fighter while someone else might like another edition. Many people have preferences across many editions.
This is an excellent point, it's obvious when looking at design that they way to address it was extremely different in particular in 3e, 4e and 5e, and that people have clear preferences, which is normal.
If anything the problem is the design philosophies are not written openly and the variants are few.
This is the part where I don't agree. The design philosophies are absolutely crystal clear when reading the rules or what the authors say about them. There is in particular an extremely enlightening section of the SAC which says: "The DM is key. Many unexpected things can happen in a D&D campaign, and no set of rules could reasonably account for every contingency. If the rules tried to do so, the game would become unplayable. An alternative would be for the rules to severely limit what characters can do, which would be counter to the open-endedness of D&D. The direction we chose for the current edition was to lay a foundation of rules that a DM could build on, and we embraced the DM’s role as the bridge between the things the rules address and the things they don’t."
This clearly addresses the difference between 3e, 4e and 5e. The problem is not that the design philosophies are not clear, the problem is that some people don't like this pointed out, because they don't like to be shown that the game they would like is not the one that has been published. And so they deny it, and belittle it instead of accepting that the game simply is as it was designed. And they absolutely want it to change to suit them, which has never happened in the history of the game. After its initial design, while there are minor changes to the game, the philosophy remains intact because breaking it would basically mean rewriting the game, which actually creates a new edition.
Which is basically what Level Up is about, by the way, based on a much crunchier philosophy, it has some common basis with 5e (all editions have something in common with previous ones), but it's a very different game which plays very differently as written.
So DMs have all the freedom but few tools and no instructions manual for modification of classes. As someone works inessential industries, freedom to do something is only helpful if you know what you are doing.
And this is the part where, while I agree with you that 5e created a lot of freedom and did not give many explanations, I completely reject this as a reason to claim the game is flawed, or even incomplete. 5e has been a massive success, multiplying the number of players by what, 5, 10, more? across the planet. This means that a huge majority of the players are NEW players, and if they managed to pick up the game and play it, is must not have been that difficult, and they did not need that many more explanation than what is in the rules and the examples of play that they find on the internet.
It's also a game where it's safe to experiment, it's amongst friends, and there are no really damaging consequences. You can learn to walk as you are doing it.
The people who complain about this, by the way, are NOT people who don't know what they are doing. All the people that I've seen making that claim are at least fairly experienced and they argue about fine details about balance. Because they don't like the premises of 5e (in general wanting more crunch, more built-in balance so that they can play it as sport or whatever), the complain on the imaginary behalf of "those poor others who don't know what they are doing and need more help". But these people don't exist, I have seen many younger players who had no real idea of what they were doing becoming DMs and entertaining their friends, with or without guidance from the internet, friends, parents, etc. and needing absolutely zero more guidance from the rules.
So can we please stop confusing things here ? If you want more crunch or innate balance for the game or some classes in particular, it's fine, it's your preference in playing the game and I respect that. And you have all the latitude you need in the game to create it for yourself, or reuse what is in great publications like Level Up.
But please stop complaining on behalf of imaginary people, and stop hoping that 5e (and the anniversary edition) will accommodate your wishes. It's not going to be a new edition, 5e is going much too well for WotC to kill the golden goose, so leave aside your hopes of innate balance and crunchiness. If it's really what you crave, there are way better solutions out there, games with a philosophy that will match your preferences way better.