I say this in every thread like this that pops up.
Use your players to help fill in the world.
Rather than spending a ton of your prep time filling in the world with people, places, plots, let your players give input.
The easiest way to do this is during play.
Erebri scouts ahead and notices smoke rising from the woods a few kilometers north.
Ask her player what they think the smoke is.
Erebri knows there is a village around here somewhere, they've been there before. She thinks the smoke is coming from that village.
Ask her player what Erebri remembers about the town, maybe an npc they met, something odd about the place, or even mundane information like trade goods.
It doesn't have to be a village, it could be a gnoll camp, but getting that input from the player gives you options without having to put in the work.
You can do this for almost everything.
The party meets an npc? Have them roll some sort of insight/perception check on the person and ask the players with the better results to flesh the npc out.
Maybe he has a limp, fidgets with something in his coat pocket, whatever.
This method doesn't always work, some players aren't comfortable being put on the spot, but most players will get better at it with time.
Also keep in mind that some players are assholes and will use this to give their characters an advantage.
DM fiat is important. Not every piece of input from your players has to lead somewhere or even be true.
Another way to use this is during character down time. Characters chat when they make camp. Someone mentions the village they grew up in? Work with them to add it to the map.
Getting their input on things not only eases your burden as a DM, it gets them invested in the world. They're gonna care more about that small mining town, Gedwynne, if they helped to flesh it out.