Since no DM in their right mind would ever allow a player to actually build Pun-Pun, let alone run him
I got most of the way through Pun-Pun once. We happen to be using the right setting though. I honestly just got bored part way through and kept myself in check. The GM saw what I was doing though and was getting really panicked because they were new to running the game and new to ttrpgs in general, but they understood I was using some kind of exploit.
wait I thought ac in dnd worked so that the higher it was the harder it was to hit you but I only played 5e so I am not sure about the earlier editions.
Yes but no. Firstly, play a better edition or even a better system. However this is a case of old and new D&D. In old low was good, in new high is good. At least for AC. This is partly to make rules more intuitive, and partly to make rules more consistent.
You can draw a pretty firm line between D&D under TSR and D&D under WotC as functionally two different things, even when we start looking at stuff like basic being wrapped up with AD&D. The original game under TSR was a game that had a lot of weird holdovers from tabletop war gaming of the time, and this is hardly the place to get so off topic as to dive into all of them, but one of them is that lower AC is better. Another notable thing is that the older editions took a lot more inspiration from pulp fiction and also classic sci-fi and fantasy.
Once Wizards of the Coast acquired the IP and commissioned a new edition a few rules got streamlined and improved. I generally consider 3.0 to be a mechanical improvement in places where it changed something from the original, but many of the additions are very much either great or terrible for the game. My personal opinion is it is generally an upgrade, but I also consider AD&D2e to still have value to play, same with 3.5e. Not 4e or 5e though. Seriously so many better games exist and 5e is not even simpler than most of them if you ever hit level 3 or higher and the "everyone else is too complicated" propaganda is what 5e pushes harder than anything. Infact there's many better and simpler games out there than 5e.
That doesn't mean everything was an improvement in the move from TSR to WotC though, and there are definitely some design philosophy changes that make the game have a very different identity. There's also the fact that starting around then the thing that was providing inspiration for the game wasn't different types of fiction and the desire to emulate the ability to have those types of adventures in the game, but rather it was being inspired by itself in many ways. The classes used to take inspiration from characters and concepts from sci-fi and fantasy novels as well as some old comics and pulp fiction. There's a lot of Conan and Tolkien in there, not just in the fact that it is a fantasy game, but also in the tone it inherently leads itself towards. Nowadays it feels like D&D is trying to take inspiration from itself. It's less about enabling you to play a character from a fiction with all the ups and downs that entails, and more about playing a hero from the game D&D, registered trademark of Wizards of the Coast a subsidiary of Hasbro.
For example the idea of a ranger comes from what a ranger is in D&D in 3e onwards and not what a ranger was in Tolkien like it originally did. This is significant because it's important to remember that at one point Ranger had the requirement to be good aligned as the archetype of the Ranger is Aragorn originally, and not Legolas like it is often made to be now, and it was less about being a hunter living out in the wilds with nature and more about being a warrior who battled evil on the frontier in the wilderness to keep it away from civilization, even while they were in a sense outcasts of civilization, as vanguards of goodness. Instead, now the idea of a ranger is a defender of nature runs around the wilderness using natural magics. A more martial counterpart to the idea of the druid. Something that occurred due to the game of telephone that D&D started to suffer from as it constantly drew upon itself as its own inspiration. It's also why a lot of the splats are so boring in newer editions. They aren't taking inspiration from anywhere but themselves. It's become too incestuous. It no longer looks outside of itself for inspiration within the fantasy genre unless it is looking at MtG. Also fun fact, at one point (maybe still is) both in number of releases and absolute page count there was more MtG lore in 5e than D&D lore.