However I don't understand why would you use Youtuber PewDiePie as an example. He surely has tons of followers, but his content is ... junk :) Far from being professional in any way.

Here is what is interesting about content: What is junk to some, isn't for others.

I don't think PewDiePie is some kind of amazing new century mind, but i watch him from time to time, and i think he is entertaining.

He is one of the creators i watch when i am looking for some laughs.

And the bigger part of the 'quality' of a content is related to the intended audience.

PewDiePie audience is Young adult gamers, therefore, he offers what his audience like. You probably think it is junk because you aren't among his audience.

If his content was totally worthless, he wouldn't be the top earner youtuber (not sure if he still is, but at least is still among the top)

Also, what i mean by professional isn't related to the subjective quality of the content, but about those that have the content creation as their main source of income, and invest a lot of time and money to improve it's quality and attract more users.

And again, 'content quality' is subjective, and each niche will have it's standards. What matters more on social platforms is popularity (within it's own niche) at the network effect.