Liberally using the massive "I WIN!" button that is the BFG has a much larger influence to drastically lowering the overall difficulty.
I don't really think so. It takes out enemies, but there is enough of the game there to show that all the BFG is really doing is just saving time and reducing the chance of player's fatigue from killing them.
Literally the only real threat that is reduced by the BFG that couldn't otherwise be so quickly are the Barons of Hell... But in the entire game you probably fight less than a handful without being provided Quad Damage, Berserk, or an area where you have the upper hand on mobility.
The game was purposefully designed so that you almost never fight fairly with any of these enemies. I mean, this is a dude that take off like 100+ and OHKOs on a melee.
Outside of Classic Levels, you're never really fighting the enemies, you're fighting the system. The system that says "so long as you're in the air, changing directions, you will seldom get hit... Oh but if you do there's at least 3 full health bars worth of pickups for you". And the original Doom is also designed around that philosophy, except you would be skipping enemies picking up powerups to survive.
I was expecting at least one of the later levels to not spoil the player with easy mode power-ups, but it was done because the enemies are not supposed to be consistently avoidable. It is obvious that game is designed around giving you the arsenal to make short work of anything youre up against. So an extra ability that breaks that design philosophy and makes you able to fully control your movement, enough to dodge fireballs like a SHUMP? That's the real WIN button there.
And anyone who has play the old Quake games even a little in multiplayer know how to use it.
EDIT: All music sounded like remakes of the Doom 3 intro music haha. But yeah, the gameplay is basically Quake in Doom's colours.