I have an example of #3 right here -
https://www.doomworld.com/forum/topic/142244-rc1-coldwire/
That MFG38 guy has been mapping for 15+ years, has led numerous community projects, yet still makes flat boxy rooms with nothing in them, except for the most boring and redundant combat you can imagine. Read the comments... it's all talk about the palette, and barely anything on the gameplay. If you actually play this piece of shit, you'd be amazed by how amateur it is... except for 2-3 maps that aren't made by MFG. Don't be fooled by the cherry-picked screenshots either.
I actually just downloaded and played this to see how bad it is.
- First map is an ugly set piece with no monsters and two secrets I couldn't be arsed to find. It's a badly lit set piece, where everything seems to be equally dark (hurts the eyes). There are no highlights, just dozens of cubes that are supposed to be cars that have smashed window textures that are just black and white, like they were drawn by a 12 year old.
- Second map starts with a wide open area of about 15-20 zombies standing in the open, while a bunch of imps try to throw fireballs from above, but can't because they always hit railings. Shotgun has to be aquired by going through all those zombiemen with your pistol. I bet the mapmaker thought he was super smart and probably hid a shotgun in the first map, wow.
Continuing on you go up a bunch of stairs and you encounter a single revenant and some zombies and since everything is completely wide open you have to jump all the way back down to get rid of the homing missiles,

.
You go into the building and you're greeted with another wide hallway with no decoration that has more imps and shotgunners standing far apart. There is a room at the end of the WIDE OPEN hallway where two pinkies cannot follow the player up the stairs, making them entirely pointless. More empty hallways, like REALLY empty and the only dangers you face are Chaingunners that will get lucky RNG hits on you, because there is no fucking cover. There is a room that looks like a C, and that one too, is empty. No reward at the end, not even a lousy stimpack. You go into a room that looks just like every other on this fucking map and you hit a switch that turns the C into stairs. Up the stairs you encounter more trash mobs and a single Revenant on ambush mode next to the wall. You walk 10 more meters and HOLY SHIT, A SINGLE HELL KNIGHT, IN A WIDE OPEN ROOM that protects a key that's just sitting on the ground and behind the key is a single tree decoration getting repeatedly lit up by two light beams, because ... uhhh ... *IMAGINATION* !!!
Now that I return to the hallway I'm starting to also notice that the floor lights at the very edge of the wall are lighting up even the CEILING. Did none of his troon friends teach this dumbass in over 15 years (or whatever experience this guy has) that you can disable the upper light by raising the ceiling and deleting the side textures?! Anyway I return to that tiny blue key door at the very start of the building, open it and ... *gasp* ... ONE angry boner in the distance surrounded by trash mobs, and they all approach you and then ... THE DOOR CLOSES, which means I can cheese this fucking room by just closing the door whenever I want. BUT NO, THAT'S NOT EVEN THE BEST PART: THE MONSTERS CAN'T LEAVE THE ROOM, THEY CAN'T WALK UP THE STEP TO THE BLUE DOOR. Then you walk around a corner and there is a single revenant again with a couple of chaingunners. They are all protecting the yellow key. They are ALL standing on the right, bunched together, while a single chaingunner is on the other side (oh my god so creative) and they have absolutely no room to maneuver, because the mapper placed dozens of ugly stone decorations with trees in the way.
So anyway I get the yellow key, but forget where the yellow door even is, because it's marked by only ONE VERY SHORT pair of yellow stripes on each side, ONE. Thank god for the automap colored doors feature in modern source ports. I open it, it's again a door that can be opened and closed freely, and inside you meet ......... *drumroll* ......... a single revenant, a chaingunner and two pinkies in a WIDE OPEN HALLWAY. You see a switch that says exit above it, hit it and LOL SURPRISE BUTTSEX by a single Revenant and two imps from behind in a wide open room, wew he sure got me there, what exciting combat. So this switch opened a door and instead of having the FUCKING COMMON COURTESY of opening a shortcut for the player, I'm forced to run ALL THE WAY around a quarter of the map to get to that door. You walk over the fake 3D bridge and you're greeted with a single, super slow DEHACKED rocket zombie, who aims at you for half an eternity before firing a single rocket. I'm on the edge of my seat here. After that you further walk 5 meters and you say hello to a bunch of Imps for no reason, because behind them is a large dark hole you could easily run into and that's the end of the map.
That's it, that was the first *real* map. The map that's supposed to show off how good you are as a mapper and an attempt to hook you as a player ... and IT FAILED MISERABLY. I'm not even going to bother to continue from here. This was painful, there is zero imagination in this. By the way the music in these two maps is bland and soulless. 100% Cacoward material right there.
The entire map looks like this, I am not making this up.