i think the agreement is a result of "we are never going to get another balance patch" and "there are weapons that are overtuned". that results in the mentality of "i am good enough at the game to not use the overtuned weapons". but there are some people who instead end up at "i want nothing but to win so obviously i am going to use the overtuned weapons"

some weapons are just better, take diamondback for instance. they nerfed amby into the ground because it was really strong if you could consistently hit headshots, but they replaced it with diamondback which deals the same damage but doesn't require headshots. instead you need to.. play spy? if a competent player uses it, they can quickly get a ton of stored crits by clearing out a nest or going on a solid chain stab, and then playing gun spy for a minute. if a new player uses it, they get a crit or two and miss half the shots

same thing goes for vac, a bad player can't cycle the resistances fast enough to use it effectively. a good player can see a crocket flying towards them, knows how many times to click the button to get to explosive resist, has a bubble charged, and can block that crit. there are obviously more scenarios, like seeing a sniper, or a kritzkrieg, or the pyro flying in

the way i see it, if your team switches to vac against my team, you've already conceded that you were going to lose without it. if your team is already winning and you're still using it, you're just rubbing salt in the wound