I agree with a lot of this. I want an option to have truly mundane PCs. Even if that means that in whiteroom spreadsheet analysis they are (GASP!!!!) 0.5 DPR less per round based on a specific set of assumptionsThis age old debate is pretty divisive. To the degree the people wanting to turn warriors into casters get what they want, they will force people like me out of their games. Despite what has been done to appease them in 5e, they aren't satisfied. 4e was perhaps the fruition of their philosophy. They want pure martials without any resort to magic to do things that the rest of us think can't be done without magic. We don't want spell like powers being performed by martials but everyone just winks and says it's possible without magic.
At this point, I don't really see how both groups can be happy with the same game. 5e has already pushed me out and it is unsatisfying to the other side. WotC is trying, somewhat successfully as 5e has been successful, to play both sides of the fence. The trend has been away from me and towards them but again it's never enough it seems until the differences between fighters and wizards is purely what things are named.
There has always been this dichotomy. It used to be worse - before 4E came along casters completely dominated the game at higher levels. In 4E (until essentials) they just gave everyone similar structure of AEDU powers and there was IMHO very little room to run a "mundane" PC.
With 5E the gap in power is less than it was, but there is no perfect solution. PCs that manipulate magic are always going to be different. Whether they're more powerful depends on too many factors, and to be honest I don't care. Casters don't completely dominate games I've been in or run (even up to 20th level).
There is no "martials vs casters" when I've played. It's a group with different strengths and weaknesses trying to overcome obstacles with whatever tools they have. The fighter may not be flashy, but they're the energizer bunny that frequently take the brunt of the attacks. Casters have the dazzle but without support they tend to be shooting stars that burn out quickly. Both support each other, they're a team competing against the monsters not each other.