What you find hard is mostly a function of what other language or languages you speak. People who speak languages without articles find articles extremely confusing in English and honestly I have a hard time articulating rules for when "the" or "a" would be appropriate.
Having a simple way to put it doesn't mean it's easy to do right.
My native language don't have anything like articles. I frequently misuse a/the in borderline cases. Or just omit the article completely..
Yet gender is super easy in my language! Each noun has gendered suffix. Once you know the word, you know it's gender. Or once you know the gender, you know the suffix... :)
Can't come up with anything on the spot. But sometimes I see text I wrote and think why I put "a" or "the" instead of vice versa. Sometimes it's just not clear enough wether this item is specific enough or not.
On the other hand, I omit article completely more frequently than using a wrong one. I find I have to consciously think if I should use an article and which article should I use. When I write/talk quickly without double checking, shit happens. Even after using English a lot for 2 decades, articles is just a foreign feature that I have to use consciously.
Sorry, I'm coming up short. But the theme, I think, is that there are a lot of cases where that sense of specificity isn't quite obvious to a learner, combined with the fact that in some cases the right choice is no article.