Too much scripted events imo is the only real biggie and it wasn't even that bad in HL2, because they weren't cinematic cutscenes, just people talking some crap, while you toss cans at them.
I'm surely no expert on shooters, but other things seem Skyway level nagging. Weapon variety? There is a pistol, a shotgun, and assault rifle, sniper rifle, nades and nade launcher + assorted melee weapon. They are and have been in all ef-pee-eses i ever played (not that much admittedly) and i don't remember them ''vastly different'' apart from their obvious functional differences or damage/range ratings. Introduction of gravity gun actually
is adding to variety. Had lots of fun with it, gimmick or not.
You are surely rose coloring enemy AIs of past. They have always been shit and are still shit. Basically not much progress has been made since doom. And i say it as a person who absolutely suck at action games. Difficulty usually comes from environmental hurdles. Like maps, where you can't get any cover, or open spaces, where you can be easily ambushed, or a guy with a shotgun camping right behind the corner of narrow one way corridor.
Puzzles are
always gimmicks. There are no ''puzzles'' in real life combat environment.
Modern games ''emphasize mobility'' way more, because they are much more open ended and you never know from where the enemy sniper could be eying you out. Old shooters where mostly corridors upon corridors, where your ''mobility'' means ''go forward guns blazing''.
Large ''spread of environments''.
- Rocket jumping and other associated jumping techniques.
- A large spread of environments, including a low-grav world.
Shoe-in gimmicks lel
Dunno what
- Very fast movement speed.
means.
Can't comment on difficulties, because i suck and always play on ''normal'' and it's enough of a challenge as it is.
But scripted events/cinematic scenes. Yeah, those things can actually ruin the game if they are the main focus like in some of the modern action vidjas. It's like devs think you want to watch a shitty B movie instead of playing the damn game.