Looking for beginner mistakes after a year [v3]

Been thinking about this for a while and curious what the community thinks. Maybe an unpopular opinion but here we go. There is a lot of conflicting advice online and most of it is from 2019.

I want to write something more comprehensive about this later but starting with a quick post to gather thoughts. This came up at a meetup recently and the room was split, so curious what the broader community thinks.

Looking for honest feedback, not validation.