Zwift is a big world in terms of numbers and there’s a lot of legitimately fast folks. I think you see people cry foul because they’re getting smashed, but they well and truly should be.
I find users overall to be pretty representative of cyclists in general in terms of fitness. The top of my Z2 is around 3.6w/kg. I’ll cruise on an endurance ride and my entertainment is the droves of riders virtually wheelsucking and then attacking only to be passed again in less than 60 seconds on every hill we encounter. Helps the time pass:)