Having practiced martial arts mostly informally for about a decade, I can say that I do not like the aspects I see in more "traditional" arts of formal ranking, bowing to a master, taking orders, etc. I had good experiences with my scant formal training, but at the same time, I prefer learning in small groups of friends from books and videos and then practicing as peers of different disciplines. My friends and I take a more "Fight Club" approach I guess, but we've all had enough formal training to not have any weird gaps in the basics. In a small group or pair of non-professionals we can develop at our own pace and focus on whatever particular techniques or principles feel useful at the time, using a gift economy approach in that whichever one of us figures out something faster helps the other catch up. The trajectory always moves away from stratification and toward mutual competency. This works really well for martial arts such as Systema and Krav Maga that orient less around specific techniques and rigid forms and more around principles and creative self-exploration. This would not work well for styles such as karate or kung fu on the other hand, as they seem to require rigid instruction, though I do practice some wing chun too informally. We focus a lot on evaluating each other through observation and sparring (so much sparring!) and testing our results (e.g. did I stop this dummy knife from stabbing me or not, how does my body naturally want to respond and was it effective). I've used this approach successfully throughout my life for both my own self-defense, defending others, and teaching others to defend themselves, without money, professionalism, authority, hierarchy, or coercion.
P.S. This intersects with my response to another question on here:
"How can I, as an anarchist, be an effective "leader" (in a non-hierarchical, anti-authoritarian sense)?"