My biggest realization while learning how to detail better is that I have a lot more fun and am happier with the results when I actually have a decent grasp and understanding of what I'm detailing.
An extreme example: when I was younger i used to be horrible at drawing buildings. They would mostly just be rectangles with some too big or too small windows and doors slapped on and just generally not look very good. This was because I didn't actually spend any time looking at or studying buildings before trying to draw them, so they were just whatever my mind's eye could come up with at the time. Fast forward several years, I actually studied in college to become an architect as my profession, and now I have a much more pleasant time drawing buildings. Not just because it's my life blood (though constant exposure definitely helps lol) but rather I just have a much better idea of the things that make up a complete-looking building: Trim and flashing about, the general proportions of windows and doors relative to like floor height, different types of materials that get used, how to break up the planes to make them look less blocky, etc. This knowledge helps even when rendering fantasy style buildings that are unlike anything I do for work, because although the shapes and materials might be different, a lot of the same concepts carry through.
Now, of course, that's not to say that you have to be a professional botanist to draw good flowers, or a professional geologist to draw good rocks or an architect to draw good buildings, but it's just kind of a reinforcement that research and references are your friend! A little bit of that goes a long ways. Some of my weak points now are drawing natural environments- I'm pretty okay at drawing cities now but still struggle with nature areas. And I'm guilty of still just kinda winging it with those areas xD;; more research and references necessary!