5e does a lot of things right, which makes sense since a lot of people-hours and money went into its development.
D&D did a lot of things right on a much smaller budget than it now enjoys...
While discussing with some friends why D&D never had a real challenger until a series of WOTC own goals led to Pathfinder...
It became clear that D&D just got certain things right pretty much straight out of the gate.
That in addition to being first, (Which is a very big deal) led to them being virtually unchallenged for over 30 years:
The 5 points that secured D&D's early dominance:
1: Easy PC creation: You could make a character and begin play in a matter of minutes. A selling point for new players.
2: Graspable Rules complexity: The first levels are not rules heavy. The mechanics were understandable. New players gradually got introduced to any additional complexity, easing the gateway for new players.
3: Easily grasped Default play mode: The Dungeon, an easy to understand and grasp mode of play. New players knew what they were gonna do right away. Explore a forgotten crypt, kill things and take their stuff.
4: Easily understood setting: Common fantasy tropes of 'Tolkienesque" Elves Dwarves, Halflings/Hobbits, Fighting evil Orcs, Trolls, monsters, etc... And Dragons! New players could easily imagine the kind of medieval fantasy land their PC's were adventuring in.
5: Straight-forward reward mechanism: The leveling mechanic is a great 'gratification' reward for killing things and taking their stuff. New players unambiguously knew how many XP they needed for the next level, and what to do to get it.
Yes you can point to the rules bloat of 2e and 3e, and how 4 or 5e fudge some of them and legitimately argue that some of those points got stretched more than a bit.
At the time; it didn't really matter as D&D had already cemented its market leader position. And now the network effect of being the 800,00lb. Gorilla in the room smooths over any rough edges the system has.
What is particularly interesting is that when you really think about things, virtually all of D&D's early competitors
failed miserably on more than one of these points.
In almost every case, D&D was delivering a more newbie accessible,
better overall game, than any of its early competitors.
Well, I could say that, um, system really doesn't matter that much, but I didn't feel like opening that can of worms.
Not a can of worms at all.
IMHO being first is
VERY powerful when it comes to RPG's.
What D&D did was also have a system that is
Good Enough that most players do not feel a compelling reason to go to a different fantasy RPG.
It takes a unique set of circumstances for
Being First + Good Enough to not be a winning advantage.
The only places that have a Fantasy game which beats out D&D that I am aware of:
Germany - The Dark Eye.
Sweden - Trudvang Chronicles/
Drakar och Demoner
Japan - Sword World
Brazil - Tormenta
Evidently Warhammer Fantasy is also really big in Poland and beats D&D there, 2e translation I think. Who Knew...
And in almost all of those cases there circumstances in those countries that helped them get one over on D&D.
I think they are good at listening what most of their customers want, and at the final deliver it.
To an extent this is true.
It does open up a very interesting question of how design changes between editions effect the way people play the game.
Then as players optimize their play for what a particular edition does; how that will effect their answers to surveys asking the customers what they want out of the game.
But fundamentally, WoTC/Hasbro did a lot of playtesting, and released the product that a lot of people wanted.
It never seems to occur to a lot of people that 5e is popular because it's giving a lot of people what they want! That all the playtesting before 5e was released, and the continual UA/Playtesting/Survey cycles we keep going through, is to make sure that we keep getting what we want.
I would point out that given how quick 3.5 appeared. The big shift 4e made, and the issues people regularly point out with 5e upon every splat release... And then their is the
cough*Ranger*cough...
I think that the word "Playtesting" does not mean the same thing to the D&D developers at WOTC that most normal people in the RPG hobby would think of when they say it! LOL!
But at this point that doesn't really matter at all. Because none of 5e’s actual issues are big enough to turn the player base off of the game.
5e has generally struck a decent balance, and has more or less done a
Good Enough job that they have largely kept their player base happy.