I don’t understand, is your arguement that a spec having very swingy performance is fine because other players can just perform at a higher level to make up for your specs design shortcomings?
People like to have agency in their own output. I mean what if every other spec had this same issue, surely then it would be easy to accept that it’s a problem right?
Looking at parse % as a whole isn’t a good way of telling how each person is performing in the fight itself since any mechanic that you get that stops you from dpsing will lower than parse % which is why you won’t typically find guilds who did a mythic fight where everyone is 90+, because someone is having to do mechanics and getting compared to other players of their spec that did not.