When I first started to use SLADE 3, I had no idea what to do in forms of map design. Should I make an outdoors level? Should I make a usual UAC lab of some sorts? How about five Barons of Hell while using your fists around a Colosseum that's poorly designed? Hence why I think before I create.
I've seen so many DOOM maps up to this point of making some myself that would end up HORRIBLY put together. I don't know how to make doors open properly, I don't know how to make something in the lines of "Collect Weapons, RATA-BATA-BANG BANG Hidden Doors that Open once collected, then BAM, cYBERDEMONS--"
...actually, that Idea seems a bit sucky, imo.
Anyways. Map making was just a pain up the wazoo, though making a basic room with adjustments to look pretty seems a bit time consuming, but cool. However, when I try to make details, it'll go in one in of two outcomes:
1. Everything goes perfect as usual.
or 2. Some vertices get buggy and screwed up and I have to restart the whole thing unless I have a backup file of that said map I am making.
That's all I have to say, either way, Doom Map Making has a huge learning curve that I have to follow in order to be part of the "Majority of DOOM Map Making".
...I'm going to guess that there are modern crap maps out there, don't wanna be part of them.