Parmandur
Book-Friend, he/him
This argument seems to come from a shallow, one-dimensional sense of "D&D can do everything" that sees "everything" only in terms of color or setting rather than how the mechanics actually impact play and cultivate the play experience. It's a bit ridiculous. It's almost like saying that Monopoly can do anything just because there are different versions that reskin the board and play pieces: e.g., World of Warcraft Monopoly, Golden Girls Monopoly, Star Wars Monopoly, Disney Princess Monopoly, etc. At a certain point, you have to realize that your game is not doing everything: it's just doing Monopoly.
So let us take the example of Ancient Rome. Just because we can slap a coat of Rome-colored paint on 5e does not mean that it can do everything. You are only establishing that it can do 5e-style Rome. But I cannot use 5e Rome to garner the same play experiences as I would from Ancient Rome Traveller, Ancient Rome Mythras, Ancient Rome CoC, Ancient Rome (whatever the FFG system is called), Ancient Rome Cypher, Ancient Rome Fate, Ancient Rome PbtA, or Ancient Rome Blades in the Dark. Because these games do things differently and will have different play experiences. The mechanics matter, and you cannot with any real sincerity tell me that 5e (or D&D) can do everything.
On other forums, such as RPG.net, you will get a lot of people who recommend using Fate to run their games. However, even one of the creators of Fate, Rob Donoghue had enough humility about his own system that he co-created to say that Fate is not good for everything nor should it be used for everything. Because he is aware of the limitations of Fate as an engine and toolkit. And yet why do so many people feel the need to be so hyper-defensive about what should not be a controversial statement: i.e., that D&D cannot do everything? Why the desperate need by some to defend the idea that D&D can do everything? What spurs that impulse?
Are you honestly arguing that the mechanics don't matter or impact play?![]()
People are a much, much larger impact than mechanics. Sure, mechanics can get in the way or not get in the way, but once they are working for everyone the interaction between people is what matters in an RPG.
5E is very, very good at not getting in the way of people playing whatever they wish. This is a big part of it's success.