One of the things I hate doing is looking back at my work from even a few months ago and realize how bad I was at writing in English, how many grammatical mistakes I was making and how ignorant I was when editing.
Nowadays, I'm trying to make an effort and improve my English in order to increase the quality of my articles. Some of you would say that the content itself is a lot more important, but I beg to differ - I think both are important in equal measures.
First of all, readability is important. Being able to publish an article that will be easy to read for someone interested in what you have to say is extremely important. People shouldn't have to reread your sentences or pay close attention to some of the things you say in order to understand your ideas.
Your readers should have a great experience when reading your articles, and it's your responsibility, as a writer, to provide them with that experience. That means using simple words that most people will understand instead of using fancy ones to make yourself look smarter, making sure you don't have a lot of grammatical mistakes throughout your articles, making sure your ideas are in the correct order, that you don't contradict or repeat yourself too much, and so on.
All those things are extremely important when it comes to how people feel when reading your content, and you should always be aware that when anyone has a difficult time reading something, it's extremely rare that those people will invest even a few more minutes trying to understand what you wanted to say. They will usually leave and search for something a lot better and easier to read.
Second, writing in poor English will make you look dumb, no matter how important and intelligent the topic you approached is. Even if you write about something like quantum physics or mathematics, not being able to write properly and making a bunch of grammatical mistakes will make people consider you stupid.
And you may say "Well, what do I care about what people have to say about me?", and I would say that that's the right mentality in most cases. However, when it comes to your content, if you want people to notice what you do and read your articles, then you should care about their opinions and how they perceive you.
If you want to make a point, if you want people to pay attention to what you have to say, and if you want them to check out your future content, then you should make sure you're capable of writing in proper English.
That usually means paying more attention to how you write everything and also editing your articles in order to remove any mistakes you may have missed.
I'm not saying your articles should be perfect. Mine aren't, I'm sure of that. I'm also not saying that you should spend hours editing your articles and look at everything you write again and again just to make sure you achieve peak perfection.
What I'm saying is that you should pay attention to more than the topics you approach, and make sure that your readers have a pleasant experience when consuming your content, and that means writing properly and avoiding unnecessary mistakes.