You don't have to go to milsim to not be able to carry an entire armoury of RPG-actually-full-blown-missile-launcher, grenade launcher, assault rifle, sniper rifle, DMR, submachine gun, multiple sidearms, plus various other alien weaponry, each complete with enough ammunition to fill an 18-wheeler trailer if desired to be stored with any sort of safety.

It was fine when I was playing Doom ][ but that's something that started bothering the hell out of me back when Half-Life came out with its believable sci-fi setting, as it kept breaking my suspension of disbelief.

"Can carry only two, maybe three tops with sidearm" seems to be the rule these days.

I think change was more so move from keyboard to also supporting controllers. Keyboards easily have 9 weapons on number keys and in some cases like quake nail gun even more on same key. Controllers just do not support this as easily. Thus move to things like wheels and other input methods.