General problem with parsing in games is its always used as an excuse for extreme toxicity. There's some who use it for self betterment, but most just use it to flex and dunk on others.
What I don't get is how people act so surprised that so many people don't use or like parse systems, and it's not even just about the toxicity that it breeds. Just think about it- when you play an RPG, say FFX, or Chrono Trigger- do you run a parser and spend hours looking up the best way to maximize damage for every encounter? Now perhaps you'll say 'but that is a SP game'. Well, when you play a game like Diablo 3, do you throw a fit when someone isn't playing the top damage class with the spells and gear set that you were told online does the max dps? If someone's using a gun in a shooter that can do 300dps when there's another gun you know can do 310dps do you blacklist that player? There's plenty of looter shooters, ARPGs and other multi player games that can be optimized that most players never will do. Parsing's like Mario speed runs- if you like it, go for it, but expecting everyone who plays Mario to be doing it for speed run purposes would be absurd.
The parsing obsession is not a normal thing in gaming, it's actually an extremely niche thing that in most games is barely if at all done- so assuming that most players want to be part of it, or want to be hassled because they didn't parse or haven't spent time out of game looking at strategies and guides is pretty much ignoring that basically nobody does that in every game, and while it is more common in MMOs than elsewhere, it's still a toxic niche that generally pushes players away because of how its proponents tend to act.
There's another thread here where people are complaining that players leveling haven't maxed out their gear before stepping into normal dungeon finder- so it's not even just about 'the most difficult progression raids'- people use guides, optimization, parsers, etc... to dump on people even in the content specifically aimed at the most casual players, and we still wonder why SE doesn't openly support a parser. And that's not even going into the profanity laced tirades that some streamers go on while they direct their followers to harass players they've outed as bad by name- only to get banned and have players try to explain why orders to pester players while dropping hard R or worse are just 'constructive criticism'. I have to wonder if the people constantly claiming that's not toxic really have a grasp on why the average player does not want to be subjected to that.