How to improve the organization of a monolith application?

I started on a new team 6 months ago, and the app is kind of a hybrid monolith / microservice architecture. Parts of it are dispersed among individual microservices, but the bulk of the features reside in a Java Spring Boot monolith.

Because of the many Resource, Service, DA, VO, helper, etc. classes, this monolith is pretty big and unwieldy to navigate. The specific features aren't partitioned into organized folders either, so you have to sift through it and judge by class name what something is doing.

I would like to try and improve on this, but I'm not sure how and in what would be a meaningful way. Would this even require any development, or just re-organizing packages?

Any other suggestions + side effects I'm not seeing are welcomed.