I am pretty sure they are all casuals besides Naofumi. I mean, they have the "knowledge" they have because they all played the same MMORPG but when it came to stuff normal adventurers should know they didn't know squat.

Also Gamers wouldn't be nearly as brain dead as the 3 stooges (Spear, Bow and Sword) generally speaking.

That's how he got into the parallel world, but his gaming style is what they're talking about here