It's incredible how it sucks people in. The skill floor to expressing yourself is _damn low_; if you can draw 2D polygons, then you can make a Doom map with DoomBuilder[0]. But the skill ceiling is high. And the ease of creation allows for equal ease in iteration. And the source ports add loads of neat little features to add even more capacity for variety.
So you start by throwing together some boxes; and before you know it you've spent 11 years building a monster of a map in your spare time[1].
The incredibly low skill floor is definitely a big part of the scene's success.
I know a number of veteran professional level designers are kinda worried about the field. So many of them got their starts playing around with the level creation stuff that frequently came with PC games. It got them interested and allowed them to walk before they could run. So they're a bit afraid a new generation might be starting from less than they had. There's some hope that maybe Minecraft and Roblox will be a younger generation's starting point.
Game development is the most accessible it's been in many decades, but level design specifically is perhaps less accessible than it was circa 2000.
Yep, as a fellow game developer (programmer) I had similar concerns... Until recently.
Unity had the issue of the high skill floor of creating meshes for scenes until recently. You can now build reasonable looking unity scenes using a process akin to Hammer and QERadiant; albeit still inferior to those, IMHO.
There's also the resurgence of interest in crunchy arcade shooters, using classic engines no less, which is drawing attention to tools like DoomBuilder and TrenchBroom.
Annnd VR tools are making complex mesh building a lot more accessible by making it a lot more intuitive.
There's definitely been improvements in level editors for existing engines. Hell, if you want to use those old editors, there are even plugins like HammUEr, to use Hammer with Unreal 4 and Qodot to use editors like TrenchBroom with Godot.
But I will say there was something particularly special about level editors coming with the greatest games of the day back in the 90s and early 2000s. Not only was this extremely accessible as it meant you could just learn level design, and not the rest of game development, but it meant you got to learn level design for your favourite games, something particularly enticing to young people. You also got a bit of a built-in audience.
The low quality typically consists of ugly appearance and ridiculous or defective architecture, which rarely impact the fun of shooting monsters too seriously: even mediocre and uninspired careless placement of monsters in boring environments results in decent combat action.
I don't see it. Take a look at Mario Maker (and more recently Mario Maker 2). There's a vibrant scene there of creators who've started with "What if the first level of SMB but one off-screen Thwomp? Is that funny?" (Yes) and ended up making one screen puzzles, decent Kaizo (in the sense of levels which require high skill to complete, obviously all of Mario Maker is Kaizo in the other sense) even some of the weird troll sub-categories, like people who all they do is make anti†, without even a "real" course for you to need it: https://www.youtube.com/watch?v=1NSDxlgMRZQ
†A "softlock" is when it's possible to get into a situation where the player can't win but they also can't die and start over, so they must either restart the game or wait for some in-game timer to count down to zero. In normal course design you should prevent this, if necessary with an "anti-softlock" where Mario assuredly dies once frustrated in this way, e.g. you miss an important jump, and Mario just falls to his death, rather than being stuck in a deep pit from which he cannot escape. But in troll design you make dying in this circumstance possible but extremely difficult, so that the player's skill in tested not only in winning, but also just in dying. This art is called an anti-softlock or most often "anti" for short and is a crucial part of "troll Mario".
That's not even on a general purpose computer, a Switch is something you might have purchased or been gifted solely to play video games and now you're a level designer, able to show off your aesthetics, pacing, mechanics and so on.
(Java) Minecraft is way beyond that because it's not even just about level design, it goes way beyond even a Doom TC. People change the physics rules, how graphics are rendered, not to mention radically changing the gameplay. I basically only play the ascend-to-godhood type packs, and even among those there's so much variety between something tightly themed like Compact Claustrophobia or Star Factory, and big sprawling do-what-you like packs such as Stoneblock, or Project Ozone. But now you're a video game programmer (albeit in Java) not even just a level designer.
Super Mario Maker 2 is a good example of accessible level creation, but for other players the levels themselves are black boxes. Yes, it's easy to create and upload levels, but downloading and viewing other people's levels in the level editor is simply not allowed on a standard Switch. This is a problem since levels in general are not WYSIWYG: they use e.g. off-screen mechanisms, hidden blocks, and overlapping entities.
It took over two years before 3rd-party software could break Nintendo's DRM and give players the privilege of seeing how someone else's level works:
I can kinda see why Nintendo did this - rip off levels were a problem in Mario Maker, much harder to do that if you can't copy the level. Notice how many poor quality MM2 levels are the built-in demo levels (which you can freely start from) with a minor tweak? That would have happened to everything.
But you're right that it's frustrating if you're starting out. Many Troll makers provide a "behind the scenes" version where you can inspect how the contraptions work e.g. adding a vine you can climb to see mechanisms "above" the level, or making something transparent or whatever.
I think trolls are the category where off-screen mechanisms are most important. In a puzzle level they're mostly an unnecessary confusion (where did that key come from? Well, off screen a Thwomp hit an ON/OFF switch and...) and in Kaizo who has time to look at everything on the screen, let alone think about things that aren't on the screen.
Of course once you're actually "Into" it there are private discords and so on for discussing stuff where people upload video, provide codes for their "Uno mas" demos (ie very short courses that show off a single new idea) and explain insights into the underlying mechanisms. I never got that deeply into MM2 but it's clear that people writing trolls for Carl or Geek are co-operating.
So you start by throwing together some boxes; and before you know it you've spent 11 years building a monster of a map in your spare time[1].
0: https://doomwiki.org/wiki/Doom_Builder_2
1: https://doomwiki.org/wiki/UAC_Invasion:_The_Supply_Depot