Give someone a notebook and a pen, and ask them to put an idea down. How long do you think it'll take them? 5 minutes? 10 minutes? They will draw a mind map or a flow chart, label it, draw connections between smaller concepts; all using just a pen and a notebook. It's the ideal way, the standard, in terms of speed & simplicity, for note taking.
Digital note taking apps try to solve some of these problems - each bringing its own variation of "the ideal way" of taking notes. Some like Notion killed simplicity and instead focus on flexibility; the result is a complex app that does a lot of things but only if you know how to use it. Others like Simplenote took the opposite side: simplicity over flexibility. The list is never ending.
Privacy is such an important issue in note taking that I am baffled by why it isn't more mainstream. Go back several centuries when there were no computers and you find state officials, and other people who cared about their notes, encrypting everything manually using various ciphers. This was a widespread practice when sending messages via pigeons or by hand. The purpose of all this was to ensure that only the intended person could read their messages and anyone who'd violate this would be severely punished.
Fast forward to 2021 and majority of the apps are still storing their users' data without any form of encryption - meaning that anyone with access to the apps' servers could read, edit, delete, or sell that data.