Software Engineering Documentation Best Practice?

Hey all, I'm still a junior dev with years of experience in IT. One of the things I've noticed since making the switch is that (at least where I work) documentation is inconsistent.

Things I encounter include incomplete documentation, outdated documentation and written process details that have assumed knowledge which makes it difficult for junior Devs to pick up.

I've had a search and a lot of what is out there talks more about product and how to document that SDLC rather than best practice in writing and organising documents against the actual software engineering and its processes.

Does anyone have any good sources or suggestions on how I could look to try and begin to improve documentation within my team?