agentorange
Arcane
Brutal Doom created a perception of what Doom is to people who never played the original which at this point is impossible to correct.
You must continue circle strafing while reloading, and are left vulnerable in this state. Brutal Doom's gameplay demands more brainpower and skill, and that's primarily why I'll never touch vanilla again. Monsters that are competent threats is a big factor. Overall there's approximately twice as many variables the player has to consider.
Edit: To add to the reload thing, continual firepower is still an option. Instead of reloading, switch weapon. Switching to another weapon (which takes about 1 second, about the same time as it takes to cock the shotgun's pump) instead of reloading is often a good tactic when you're overwhelmed. Furthermore there are still weapons that do not reload, like the BFG, chaingun and super shotgun (or it does reload, and did vanilla, technically).
This strikes me as adding needless complexity, and complexity in and of itself doesn't make anything better. Same goes for the notion of how the game is more "challenging" or demands more skill because of these additions. You could also add realistic weapon recoil, fatigue, the ability to go prone and any number of other mechanics, which may make the game more challenging just by virtue of forcing the player to keep track of more elements, but as you do so the game gets further and further away from what made vanilla Doom great, primarily its tight, no excess design.