I’ve had to do a lot of this recently. The players I GM for started out very inexperienced. Some had never played and the only ones that had played had only played limited amounts of D&D 3.5 Edition or earlier. Part of the hardest thing with being a GM for new/inexperienced players is that you have to be the facilitator for your players. You have to meet them where they are, but you also have to encourage them to move closer to clearer and more creative and fun gameplay.
People above have said great points! I would absolutely agree that the keys to getting your players more comfortable, expressive, and creative are communication skills and probing questions. The issue with inexperienced players, though, is that most don’t have either of those skills developed very well. Your players may be able to express how they feel, but they may not be able to say definitively, “This would make the game better.” They can tell you how they’re feeling, though, and as you play, you can course correct and experiment. Don’t be afraid to fail in what you try. Giving players and yourself tangible experience goes a long way in communication and in gameplay.
Likewise for probing questions, your players need to know early on that there are no wrong answers to questions and that their answers can provide a lot of depth and context to the world. A lot of new players know the importance of these questions, and that can scare them. That’s where the difficulty comes in. You have to start with low quantity and low risk questions. Even the freshest players know that they can go buckwild and burn down a church without warning or something, but the GM and other players have to express to each other things like “What does that look like?” or “Does your character carry ?”
You need to show the players that whatever they add to the story is cool and good and that you’re glad to have them with you. For some people, it’s hard for them to answer questions like “Who is in this town?” or “What are the daily religious practices of your church?” because those have lasting, world-changing impacts, so start small if your players are having trouble nailing those down.
Most importantly, though, appreciate your players. Tell them when they do cool shit. Talk to them frequently and often about what they do. It makes a world of difference in player experience and in game quality.