For many years I have been taking notes in https://workflowy.com/ . The extreme simplicity of the tool coupled with the way that nesting brings structure to my thoughts is ideal for me.
I used to be a long-time user of Workflowy (since 2012), but I've recently switched to Dynalist ( https://dynalist.io ). It's more actively developed and deviates a bit from the extreme simplicity of Workflowy. I haven't looked back though. :)
I've tried Dynalist and had numerous performance issues. Talked to developers a bit and switched back to Workflowy.