Nowadays everybody is a writer. Some people write poems, other write short narratives or long novels and most of them think they are talented and good at it. There are many ways to publish everything on internet but where goes the quality? There are hundreds of indie authors which is not bad at all but how many of them are real writers? According to my experience i think that no more than 5% write something that really worth buying it. What is your percentage?
No, writing is not easy. Allow me to illustrate on your question some of the things that go into writing.
The sentence "Nowadays everybody is a writer." Doesn't truly convey what you're trying to say here, I'm guessing. Since there are obviously illiterate people about, and you don't include yourself in the scope of the people who consider themselves writers, then your sentence exaggerates a little too much. A more effective sentence would qualify it somewhat and include something to limit the breadth of the inclusive set. Something like "it seems as though." And the colloquiallism "Nowadays" when used on a forum which is frequented by non-American member is going to go over some people's heads. Also, since you seem to be implying that a majority of the people who refer to themselves as writers, actually aren't, then the verb "is" is a bit weak. You really should go with something a little stronger. Maybe "pass themselves off as" I would have gone with "These days, it seems as though everyone passes himself off as a writer."
The second sentence is a little more difficult. "Some people write poems" is a little too specific, because poems conveys the sense that they write completed pomes when if fact they probably also write incomplete poems. I would go with "poetry" in lieu of "poems". Also, the "people" in "Some people" is understood. It's obvious from the first sentence that you're talking about people, so I'd drop that and go with "Some write poetry," to start the sentence. The next part is a little convoluted. "other" is singular. You're talking about a group of people, so it really should be "others." You've got the repetetive "write," but that's not too distracting, so let's leave it in there. The word "narratives" is ambiguous in this case. A narrative is a part of some larger work. Since your next item on the list is "novels" I think you can safely go with "short stories," which is what I'm assuming you meant. The "long" in long novels is odd. A novel is by its very nature longer than short stories, so I think you were trying to convey the sense that people write everything from short pieces to very long epics, but since you didn't set that up with an "everything from".."to long novels", it doesn't really work. Following that, you are missing a punctuation mark. Probably a comma, but since I'm not sure how that second sentence was intended, it may also be a semi-colon. The last part of that is redundant. "talented" and "good at it" are really the same thing. You're wasting words. I'd pick one. If it was my sentence, I'd go with "Some scribble poetry, others everything from short stories to epics, and most of them think they're talented.
The third sentence is quite convoluted. The "There are many way to publish on the internet" isn't really clear. It's obvious that there are many ways to put your words on the internet, but I think you mean to imply that it is easy to put your work on the internet and sell it for a price, rather than to say that there are many ways to do it. And I'm also pretty sure that you don't mean to confine it to "the internet," since it's just as easy to go the POD route (print on demand). I would have gone with something simple like "It's easy to publish." The next part of the sentence is a little off. "goes" is a verb of motion. "Quality" is typically defined by volume rather than motion. Something has more quality or less quality. It doesn't have up, down, left, or right. I would have expounded a bit and gone with something like "Since it's so easy to publish, what happens to the quality of the work?"
That's just the first three sentences, and they would have to be polished several times before I decided whether or not to publish them. As to your other question, I don't know the ratio of bad writing to good, but I believe readers have the option to return books they aren't pleased with, and some things will be "worth" buying for some, while they won't be worth it for others. What I'd do is read the samples and the blurbs, and decide from those whether you think something is or isn't worthy of putting down good money for.