Westenberg: Be a Magpie
Every single one of these systems works for someone. Getting Things Done genuinely transforms lives for people whose brains work a certain way. Bullet Journaling provides structure that some people desperately need. The problem comes when we treat these systems as complete, hermetically sealed units that you either adopt wholesale or reject entirely.
The magpie knows better. It understands something that productivity gurus spend entire books dancing around: good ideas are where you find them. The optimal approach isn't to pledge allegiance to one system and defend it against all competitors. The optimal approach is to steal liberally from everything and build something that actually functions for your specific brain.
I think I'm a Magpie.