Honest question: What exact situation does this game put you in as a DM that needs to be fixed?
The fact that, consistently, martial characters feel like they cannot participate. Even when I specifically design encounters to highlight their strengths... the casters dominate.
I once had a puzzle I set up for my players, they were repairing a massive arcane engine. I had a barbarian, so I made absolutely certain to include big heavy things that needed moved. The barbarian realized it was a puzzle, said "Oh, no combat? Well, nothing I can do to help then" and even with me all but saying "pick up and move the pieces!" and forcing him to participate, he felt there was not a single thing he could do that was worth even attempting. Because the magic-users had it covered.
Blame me for poor encounter design. Blame the players for being bad players. But what I find strange about all this "but it is the DMs fault!" "But that is the players fault!" is that it happens to multiple different unconnected players, it happens with multiple unconnected DMs... and in fact the only common denominator is the game. That game we are told CANNOT be at fault. The game that we are told would run perfectly fine and never have this issue if we just had Good DMs who played the right way.
Heck, another example? I'm playing a solo game as a monk Sheriff. We made up the town, and set things up so my character would have things to do... and immediately we had to adjust things, because we absolutely needed a cleric who could cast healing magic. And when my sheriff encountered an undead who challenged them to a do or die... my character called for the cleric, because it was an undead and other than playing the game the undead was designed to win, I had no options. And going forward with my character... I still am going to have no options. I have one tool other than punching things, and that's because I'm a tiefling and have magic.
And please, stop twisting my words. I never said anything like the hyperbolic statement you gave. I stated that at this point in the game's development, the DM has more control over balance issues than the rulebook. Adult communication between the people at the table have more fixes to the system than anything a rulebook can come up with.
The hyperbolic statement was a statement of the feel I get from these arguments. Because it is always the same question, "Don't you trust your DM?"
If you answer yes, "Then, there is no problem."
If you answer no, "Then why are you playing with them? Find a better DM so you can answer yes."
I'm all for adult communication between player and DM, but I also don't think it is fair for every single DM to have to homebrew solutions to fundamental flaws in the rules. They may be able to do so, legally, but it is an undue burden. And I'm trying to fix that burden. Heck, I even made an entire series of posts that I linked in this thread with solutions, as demanded by the people in this thread who called for people to stop just whining and actually do something. So I did. And yet... interesting how very few people seemed interested in looking at those solutions, how instead they just want to claim there is no possible problem, that the REAL problem is bad DMs playing the game badly.
Here is a claim: Each table is different. Your problems are not another table's problems. They have their own issues because the game has a bazillion combinations of races, classes, powers, spells, settings, monsters, players, DMs, dice rolling, and chemistry.
So when your table does find a problem (like the martial class isn't as shiny as the wizard), and you see other tables having the same problem, but you also see many tables that are not, then do exactly what you are doing. Try to find solutions. But try to do it without discounting the opinions of others that do not see the problem. Do not simply think they aren't as experienced as you or don't have your knowledge of game design. They do. It's just their combinations at their tables don't have the same holes.
So at what point is the reverse true? At what point is there an actual game design problem that needs addressed, like Moon Druid Wildshape to just randomly come up with one. Or Warlock Pact Magic on a Short rest, that the designers need to actually address. And what if someone says that due to their combinations don't see that problem, do we keep the status quo that that table has, and tell the everyone else that nothing should be fixed?
Or can we accept that this problem, which has existed for years and years and years, which gets brought up time and time and time and time again, might move beyond a simple table issue? That maybe upwards of 50% of tables run into this at some point. That seeing patterns in the questions commonly asked points to this being a problem. After all, you know what I see all the time looking at Reddit threads and such? People asking how to handle high level casters. People saying "I reached X level, and now the casters in my game can do X,Y,Z and I don't know what to do." You know what I never see? Not even once? "The fighter in our party hit X level and now they are so powerful, what do I do?"
Maybe, just maybe, there is an actual hole here. Maybe, just maybe, we have legitimate concerns and would like legitimate consideration.