No. Definitely not. Although you’d have to define “competitive” pretty tightly first to really nail that one down. But for any definition I could consider reasonable, the answer is no.
You seem to be focusing on M+ from +10 to +17. From some numbers I looked up recently, less than half of all players, and maybe down to a third, have EVER completed ANY +10, even once, even boosted through, in BfA or Legion, much less regularly.
+15s would be even lower, ofc, maybe 80% of people have never done one.
And yet MOST people never do any of this and play the game just fine (and yet without half the complaining we see from people who … nevermind 
)
I saw a distinction a while ago I thought useful: many people play WoW as a vaguely competitive game, but many more treat it as a pastime, like knitting, watching TV, kicking a ball around in the local park.
As long as the game is giving you what you want, everything is fine, even if someone else wants and pursues different things. You seem to want to get competitive, but you’re not there yet. It’s not the game’s fault. It’s probably not yours either; maybe you just haven’t found the right ladder to climb yet.
So you may be expecting an unrealistic standard of yourself.
Are you trying your M+ in raw PuGs, or have you tried to form a regular group? Pugging is a terrible way to learn. Try joining a community like Scared of Dungeons
where you may be able to ask more experienced players for tips. Just don’t expect them to do your work for you.
OK. This truly baffles me. There is more information, more easily accessible, out there about how to improve and succeed in WoW than there is about most school and college courses.
Unless … I recall a Richard Gordon quote about med students who were never seen without a textbook under their arm. He observed that they seemed to have a theory that they could absorb knowledge through their armpits. 
Like any other skill, you learn what to practice from external sources, but you get better only by doing the practice itself. Reading books about running technique won’t get you achieving a 5-minute mile.
I do grant that so much of the information is about the latest instance tips and tricks that it can be hard to dig out the more basic techniques like position, movement, keybinding, keyboard + mouse co-ordination. It’s there if you look for it, though.
What are you doing to practice, and work on your various weaknesses? Have you even identified the areas in which you are weak? How do you hold up in Proving Grounds? (No, it doesn’t cover everything, but if you are weak in basic class knowledge, it will expose that.)