You can put as much or as little work as you like into the details of the setting and NPCs and plots and history and whatnot but it all boils down to one thing:

Players experience the setting through you.

You might have the most wonderful setting in the world but if it's all in your head and not conveyed to the players, it won't be much fun. Unless you want to sit down and write a campaign setting book and give it to the players your entire focus has to be on how the PCs will interact with this setting. This applies to all games. With established settings, player knowledge can help make up for lack of GM description but in the end both homebrew settings and premade ones need the GM to bring them to life.
Keeping this in mind has helped me with GMing.

The idea of throwing in a lot of colorful NPCs, a few plots and some random encounters works surprisingly well.