I've DMed a Basic Campaign - DnD.
I've DMed a 2e standard campaign with Vancian casters - DnD.
I've DMed a 2e campaign via Skills and Powers with spell points, obnoxious crit tables and absurd house rules - DnD.
I've DMed 2e Dark Sun - DnD.
I've DMed 2e Planescape - DnD.
I've DMed 2e Ravenloft - DnD.
I've DMed 3e RaW - DnD.
I've DMed 3e Planescape - DnD.
I've DMed 3.5 with a thousand and one UA rules and Bo9S - DnD.
I've DMed 4.0 RaW - DnD.
I've DMed 4.0 with house rules to PC build to tailor for 2 people - DnD.
I have decades of refined opinions on what mechanics I felt created the best game from behind the screen. I have decades of refined opinions on what PC build rules provide the best framework for my players favored archetypes. I have all sorts of opinions. But curiously, none of these opinions on mechanics have been tethered to some notion of what DnD is. This is likely because I am much less Hindu than most. I have no problem slaughtering any mechanical cow and eating it with bacon and blue cheese so long as I have wizards, warriors, swords, sorcery, thieves, assassins, fallen empires, ancient ruins, dragons, beholders, giants, orcs, goblins, mind-flayers, demons, devils, verifiable Gods, elves, dwarves, halflings, gnomes...and on and on. Give me a standard setting that is some sordid marriage of feel of American Frontier, Feudal Europe, Mongol-ruled Eastern Asia...and a few high fantasy oddities. Whether I have THAC0 or BaB, flat math or swingy, poorly QCed math...Vancian, Spell Points, Saving Throws, Defenses. Give me 4 little boys (masquerading as grown men) at a table with dice, books, and DM screen with fiddly bits on it and its all DnD. Some mechanics work specifically toward my favored ends/tastes better than others...but its all DnD.
I have to admit, I find most of what I read in these type of threads extraordinarily distasteful at best and willful or ignorant provocation at worst. Grognards, such as myself, do not own this brand nor do those new to the hobby with 4e.