An example they brought up is the alignment system: it's one of the most criticized aspects of the game, especially with regards to mechanics. Nevertheless, it's baked into the culture of D&D by now ("What would Batman's alignment be?") and while getting rid of it might improve the gameplay, it would be removing something core to the game experience.
https://trends.google.com/trends/explore?date=all&q=%2Fm%2F0...
(not sure why it's showing results for pathfinder before 2008)
Then there is Traveller, Runequest, Tunnels and Trolls, Car Wars (with Truck Stop etc) and rather a lot more.
3e (more specifically 3.5e) was extremely popular. There's now a ruleset called Pathfinder made by another company, Paizo, that continues the style of 3.5e and is mostly compatible with it (though it has its own core rulebooks and most people I know don't mix 3e and PF).
4e wasn't as well liked but it still had mostly good reception. It was very polarizing to many players. This obviously isn't the space for a debate about it but I think the biggest cause of complaints are the way the combat system was overhauled. Many people compare it more to a modern RPG video game rather than a pen and paper one.
5e has had a great reception from old and new players. It's rules are definitely closer to 3rd edition than it is to 4th. Though it brought in a lot of quality of life improvements from 4. For example while it makes sense that 'Hide' and 'Move Silently' are two separate skills, it just means a rogue has to split their skill points between two things. There's not many scenarios outside of comedy where you give a character 'Hide' but not 'Move Silently' or vice versa. 5e has merged both of these into a single Stealth skill.
All the editions are still considered Dungeons and Dragons though, and not separate games (of which there are many wonderful ones, some of which have their own 1e, 2e, 3e, an so on...)
To be honest as a DM/GM I generally threw out the rules as soon as they got in the way of a good narrative.
I'm quite tempted to give it a dabble again ...
5e seems to be designed with that in mind. Bonuses are largely replaced with the "advantage/disadvantage" system which gives the DM much more leeway in determining bonuses (beside simplifying the mechanism overall). Skills are greatly simplified and reduced in number, and partially replaced with "Backgrounds" which are 100% DM fiat.
Example from my first 5e session. "Use Rope" is gone, but my character has the "Sailor" background. So by DM fiat I was able to identify the condition of a rope. No dice involved.
As an example, Pathfinder simplified lots of different combat rules under the Combat Maneuver system (CMB/CMD). 5e simplified them even more, simply as contested skill checks selected by GM fiat.
Unfortunately, as Paizo seeks to grow its business and publish more content, they tend to keep adding special rules and things that kinda distort that original accomplishment.
The tighter your grip on the threat of D&D, the more mid-40s nerds slip through your fingers!
Imagine this hypothetical person wants to spend as little time as possible learning and on details, and as much as possible on creative experiences.
I'd make a silly wager that the net time saved by using 5e rules would outweigh the cost of learning them.
Though that kind of reinforces the point.
Course some of us will sit there and say y'all should just be playing 3d6 instead, but I digress...
Aside from network effects, the rules are much easier to use in play without referencing fairly arbitrary tables; there's a lot of streamlining and consistency that lets them handle more situations with less lookups, different mechanical subsystems, and fiddly bits.
Notably, a unified success mechanic that covers skill use (including what were “thief skills” in core 1e, as well as “nonweapon proficiencies” from some of the 1e supplements), attacks, ability checks, and saving throws is a big improvement from 1e (D&D has had that in some form since 3e, though.)
Each system provides both power to tell stories and restrictions on what stories make sense within the framework. 3.5e, for example, was a high-powered but extremely clunky framework -- it let you build epic creative experiences, but often got in its own way. 4e was a lower-powered storytelling experience because it was so focused on "balance". (My experience doesn't go all the way back to 1e so I can't comment on its specific strengths and weaknesses.)
One thing I really like about 5e is that it's quite streamlined, but has a variety of options integrated into the core game. Things that were clunky in prior editions (like prestige classes in 3.5, or ritual-casting in 4e) are now supported smoothly. So it's high-powered but also kind of gets out of the way.
EDIT: I think the fear of learning new rulesets is itself a reaction to the overly complex early-edition D&D rules. You have to learn so many different types of mechanics and try to keep them all straight. You have a bunch of different bonus types and have to learn which ones stack, and then try to maximize the overall stack. 5e is actually really quick to learn, and as such, it gets out of the way of the creative storytelling experience a lot more than earlier editions.
To add to this, one minor thing I like about 5e is how much freedom the game explicitly gives the Dungeon Master. Obviously nothing is truly different, the DM is god in every edition. But I've played with many, many DMs (usually new DMs) who will refuse to do something fun because it goes against some way a rule is written in the book. Even if they and the whole party wants it to happen, it would be breaking "the rules".
The first DM I ever played with actually would never let us call anything a rulebook. It was a Player's Handbook or guidebook, or what have you. Because as she said, she was the rules, not the book.
I think that really helped form a mentality of "Fun First" when I run a game. The 5e books felt a little heavy-handed at first, every third spell says something along the lines of "If the DM chooses". But it's already helped me in some real games as a player, where the DM can do what they want and not what the book says, because by doing what they want they're still doing what the book says.
Also 5e is AMAZING for giving out a TON of story hooks as part of the character creation process. Sure, you and your GM may be old pros who know how to make a story, and that’s great. But if you’re having an off day, or bringing in some new players who don’t know how to prepare the seeds of a story, it’s pretty damn useful to have all these hooks lying around.
Everything is generally streamlined, you will mostly be rolling a d20. Other dice show up for your HP and damage, because it’s just not D&D without that handful of weird-shaped dice.
AD&D/1e (and other pre-5e versions) books are available in hardcopy and PDF, new, today. There's certainly a network effect benefit to 5e today, but 1e isn't limited to people with battered copies from the 1980s.
It's similar to programming languages - there's an ineffable quality to a language that makes you just want to use it (or not). I knew someone who picked up DarkBASIC several years ago; I could have suggested he get into Python or something more "mainstream", but I think the right choice is the one that makes you want to sit down and work on your project.