I think more people should read about the profile of toxic/abusive people yes. Arguably, the label "narcissist" to apply to these people is helpful as a kind of shorthand, google search term, etc. I certainly found it extremely useful and enlightening when I was dealing with my ex who absolutely fit the internet definition of a narcissist. Whether he actually has a diagnosable disorder - several years later I couldn't begin to say. And I'm not really sure in hindsight whether having the commonly used term cross over with a personality disorder is helpful or not. It ends up blurring truth and exaggeration, armchair psychiatrists and legitimacy. If the "internet diagnosed narcissists" are not really sufferers of NPD, then it adds stigma and potentially unhelpful/incorrect information to a real disorder. But on the other hand, if they are following the profile so exactly, it can also be useful to look at clinical information as it is very valuable information for anybody stuck in the very confusing position of trying to relate to somebody like this.
So I don't think it's as unhelpful as everyone makes out. I believe if you do think it's applied to "everyone" or bandied about etc you probably haven't had a close personal relationship with somebody who fits the description, and therefore you probably don't really understand exactly how discombobulating and all encompassing it is, and how much it feels like a raft in a storm when somebody else can say "Yes, I know what that's like, my experience was like that too" and describe the profile of a person so exactly that you would swear they had been dating the same person.
I've only experienced the same sense of relief and understanding like this twice. First when I read the description of a (so-called) narcissist in relation to my XP, and second when I read the description of inattentive ADHD, something I was diagnosed with myself aged 27, meaning that my life for the preceding 13 years suddenly all made sense.
But on the other hand, I know that both with the narcissism and the ADHD, and so presumably for other similar things, for a little while after you've been through that kind of world-changing revelation, you can get a bit obsessive about it. Suddenly you're wearing ADHD- or Narcissist-coloured glasses, and everyone who has a slight hint of tendencies seems to be glowing brightly shouting out to you "It's everywhere!!" It comes from a place of kindness - you have experienced such a weight of change from recognising something that was important to you that you want to help everyone experience the same kind of thing. And in reality anything that affects ~1% of the population isn't rare at all, that's a huge number. And everyone has some kind of mystery, some struggle, or some secret. Interestingly 2 out of 3 of the "narcissists" I have known I would be borderline for saying they probably have severe ADHD - either on top or as an underlying cause for the behaviours that don't seem to make sense.
It dies down after a while, though I do still find that I can spot "narcissists". Whether it's a made up internet definition or some real thing. I can spot people with that behaviour/personality profile, I find the ways they act to be quite predictable even though they appear erratic in comparison to how most people act, you can see the dances people do around them as well. I honestly don't think 90+% of people with that profile though would ever consider themselves to have any problems, even when it is plainly obvious to people close to them that they have pretty severe problems, patterns of broken relationships, messed up jobs etc - because they have such a skewed vision of reality that the phrase "if you're the common denominator maybe the problem is you" simply doesn't occur.
And narcissists usually are extremely likeable to be around, at least while you're in their good books. That is exactly part of the profile!