Tbh. There is no “clear cut” definition of average or casual player.
Everyone has their own criteria on whats average or casual and whats not.
Some base it on difficulty = aka, anything above LFR is not casual anymore. Others base it on time commitment = aka you are still a casual mythic raider because you log in to raid once a week versus other hardcorers who spent their time m+ spamming on non raid nights and etc.
Everyone has their own ruler which they use to measure “casualness”.
Depends on the context where those numbers got generated. I also got some grey/green parses on a few mythic kills(first kills). Now. I spent more time dodging and dealing with mechanics and possibly covering for others just to finally get that boss down instead of timing “all my CDs in perfect synch for max deepz”. Does that make average? Who knows…maybe.
But pure numbers wise? “haha u grey/green parse u bad, boosted hahaha lool”?
Never said it was bad, i said it was below average numbers wise, you’re the one who was presented with numbers and auto jumped to the word bad. you can defend it all you want but it aint even average in its own groups, it’s usually either dead last or dead full stop.
The thing I love about WoW is there is no right or wrong way to play. If you don’t want to do M+/Raid/Pvp etc then that’s fine. If you want to potter about doing casual content and collecting, that’s fabulous. If you want to be a complete sweatlord and go for high logs, high end game content, CE, Glad, M+ Title etc, that’s also fabulous. If you are somewhere in between or dabble with various parts of the game you are also doing fabulously!
It’s the same as my profession alts are paladins etc and the amount of judgement I get for them not being various classes is daft. I don’t care. It’s my hobby, my gametime, I will spend it how I please.
There isn’t one, as Lynlia said earlier it varies from person to person what they consider casual.
Some base it on time spent in game but I am not someone who agrees with that. You can be casual or hardcore and still spend lots of time in the game.
Personally I feel it’s reflected in what content you do. So to me casual is doing stuff that’s easy, old content farming, open world stuff, lfr, lfd, random BG etc. They don’t do high end game content. They may dabble a bit with content above that, or not at all.
There is no consensus. I have a friend who considers himself the filthy casual. He rarely ever ventures into anything harder. Plays purely to collect but has recently fallen out of love with a lot of that. A friend helped him get KSM and it’s his first one.
Simulationcraft and other repositories like QE Live have faulty databases, algorithms, calculations and therefore outcome.
Guidewriters and Streamers or even the R1 persons are not there because of skill but because of time and no job or education worth for a skillful job.
Meta is perception, as Ian can also be cited. The current perception of meta exists because of unsuccessful adaption approaches to calculation of the perfect gear, stat or talent synergies in optimized dungeon routes.
The playerbase of people that can mathematically optimize for it is just not existent in games
, have some 
and get ready to watch the show.