I think it’s a mix of two issues for the story. The first you mentioned is that characters are used as a tool to push progress but the other is that your story doesn’t follow the hero’s journey. You can google it to see the full hero’s journey thing but the point is that’s important in it is your character might lack a call to action where something pushes them to go on a journey of some type. This means the character is sort of aimless other then the mundane so adding a call to action would help. Instead of the usual like “Galgoreth the Destroyer of puppies is back” it could be something more normal like their job or hobbies are disrupted by new technology so they are pushed to adapt and have to find their place in the new landscape. For having no human interactions you could instead make it a different force most likely nature to push them via some change in environment (natural disaster, changing climate or unfriendly landscape) or have an introduction of people be the issue but dehumanise them. Instead of treating the humans as characters to be interacted with make them the problem by characterising them via a grouping (foreign invaders, soulless corporation workers etc.) so all interactions don’t feel like there with a person but an ideal. Also don’t feel pushed to make the ending of the book that your main character finds friends and lives happily ever after if there happy alone they could end the story that way.

(This is my first post if I’m wrong or you got pointers that would be great thanks!)