An excellent article and well worth some more examination.

The TL;DR: is that during the nascent period of development for #TTRPG, the "does system matter" question, built on the bedrock of the idea that "D&D can do anything, so why try anything else" was already a thing. https://twitter.com/docetist/status/1358499272916754433

Not just a thing, but already acting as a divisive force in game design as it does now.

The aspects that it's missing is a chronological element in the form of looking at D&D's trajectory prior to the 3e rebirth, and a look at why people were actively choosing other systems.

One thing I do agree with in it is the idea that the system you're first exposed to is formative; but I would refine that further to "the first system you play extensively in" is formative.

Anyways, back to the missing parts. The idea that "D&D can do anything" is a fallacy.

Why? Because to make it "do anything" often requires extensive rewriting of the rules and the introduction of home materials to the point it's no longer actually "D&D" anymore. Rolemaster and Palladium are notable systems that emerged from deficiencies in D&D.

So the primary defense is that of you change it enough, it can do anything; not really something the bulk of gamers are into. It's akin to saying that Super Mario Bros. exists, so why play other video games when you can fill in the gaps yourself and layer on a story so it...

...seems like you're playing Final Fantasy.

So this leads to the trajectory. D&D was huge, first, and immediately under fire. It turned out that not all nerds had wargamer levels of time to spend "painting their army", and the skimpy, kludged up rules and less than pro level...

...layout work was all working against them. But despite credible challenges, it took over a decade from the release of AD&D for the cracks to really start showing. By the 90's, a White Dwarf poll showed that just over 50% of respondents were playing D&D of some sort. The rest...

...were playing other games. But notably in that D&D group, there were people playing OD&D, BECMI, AD&D, and 2e AD&D. The implication being that significant parts of the gaming world had ceased buying new books and weren't participating significantly in the gaming economy.

So at this point, D&D was literally on the ropes because, quite literally, "System Matters". So why were people choosing different systems?

Well, for one, it's easier to buy a new wheel than try to reshape/reinvent the old one. Then there was flexibility. D&D, when compared...

...to its competition today and in the period in question, is relatively inflexible. Flexibility is, as pointed out in the OP's article, found in the players and end users. It's not an organic component in the game. Other games offered more flexibility. In terms of both their...

...mechanics and storytelling capabilities. To use a modern example, I can use Dungeon World to retell IRL mythological stories without significant alteration of things. Jason and the Argonauts is viable out the gate. D&D requires an extensive restructuring of the myth...

...to match it's level/threat matrix or for me to throw out the bulk of the rules and introduce my own.

Then there's the perspective angle. Different systems offer different perspectives and conceptualizations that can change how you look at gaming, adventure design, and more.

D&D was and is, at its core, a squad to platoon level tactical wargame with a plot overlaid onto it as a reason to move dungeon to dungeon. Sure, as pointed out, the players/DM can alter that to a degree, but it's still the foundation of the game. Even without switching genres...

... playing non-D&D mechanics derived games can be mind-blowing for people used to D&D.

The last thing I'd like to touch on are the narratives that protect D&D by convincing people not to try other games. Because wow, they are old and they are tired.

1.) D&D can do anything!
Not without a lot of sweat, blood, and ink. Odds are there is already a game out there that will meet your needs better.

2.) Popular means best!
It really doesn't. Popularity in media of any kind seldom has anything to do with quality per se. It's...

...more a function of capturing an audience then keeping them captured by shouting so loud they don't notice other options while creating a sense of belonging.

3.) D&D was hard to learn, who has time to learn a new system?
Yes, there are people who have specific issues that...

...actively prevent them or hinder them in learning a new system. But many systems are much easier and smoother, with much shorter learning times and shallower learning curves.

4.) It's hard to get people excited about other games!
Is it? Or are you approaching presenting the...

...new game with a defeatist attitude? Excitement is contagious. Hype these other games up and avoid the "like D&D, but..." pitfall and you're going to be amazed how people start vibing with you.

Anyways, this has been a long ass thread, I need to go do fitness now. Take care!