That analysis largely misses the fact that many topics, like skills, were completely undefined in early D&D. Fighting men fought, clerics healed and disposed of undead, and magic users cast arcane spells. But when it came to knowing things or doing skillful things that weren't encapsulated in those 3 activities above, everything else was fair game without limits and boundaries except what the DM decided to invoke. Kind of more like improv acting, planning, and debating with the DM than it was a game.
All of the elements we now see as skills were just not part of the game back in the day. One of the things early competitors like Runequest did was say "hey D&D, you're ignoring that more happens than just killing monsters in 10x10 foot rooms, so we added a skill system."
When that concept finally made it's way over to D&D they could have said "OK, the rule for 'do anything' is roll a dice and add the right attribute bonus'... Or they could have divided it up between classes and group roles to preserve the very point I am talking about: each player sits down with a clear role and sense of purpose because this is a game first, a roleplay session second.
D&D 2E did a skeleton of that, D&D 3E more heavily took from competing RPGs but then limited your access so that no one could do everything - leaving each player with a clear sense of identity at the GAME table.
That's why MMOs that are the most successful look more like D&D than they do like GURPS. FFXIV is the extreme, and the #1 MMO - you can't pick anything other than minor armor buffs. WoW has a diverse talent pool, but these are like class feats. The vastly less popular #3 and 4 MMOs (Elder Scrolls and Guild Wars) are also much less clear on sense of purpose. While ESO has the near Runequest model of "everybody gets to do everything all the time", Guild Wars 2 has clear classes and builds - but the game itself is very fuzzy on what to do with them and ends up leaving players with... the number one complaint about GW2: WTF am I doing here? What is my purpose in this group?
Narrow choices to define a clear role just makes for better gaming.
Not everyone can be both the goalie and the offensive kicker and the main blocker all at the same time. If they could, the players would wander around the field wondering who is doing what and when.
If the GAME side is not important, then a person's best tRPG choice probably is Theatrix - which if fully aimed at roleplay. Too bad it coupled it's setting to an 'Adult NSFW' comic book and so became obscure the moment it went to print. The actual core book which didn't have the setting was a great design for people that don't want the game interfering with roleplay. It's the purest 'anti D&D' RPG ever, even more than the 'Amber' game was.