I see “solo” and “self reliant” as related but not necessarily the same thing. Let me explain.
Self reliant means a diver takes care of themselves in all aspects of diving including making sure their gear is all set and not in need of any outside assistance, broken parts, missing components, etc. This includes all gear from head to toe, they are self reliant and don’t forget stuff etc.
But self reliant divers can still believe in the buddy system and team diving, however they are skilled enough to be completely self reliant outside of a buddy team if the occasion arises.
A solo diver dives alone and has to be automatically self reliant in every aspect of diving. There is no one else there to bail them out of any situation including a broken fin strap or a forgotten compass, or an entanglement, panic control, OOG, etc. They are 100% on their own.
So the pecking order in my mind would be:
0. A solo diver that is a complete idiot, not self reliant in any aspect of the term, and is an accident waiting to happen. Notice I labelled them a “0”.
1. Complete amateur diver in need of everything (gear set up to DM holding their hand).
2. Needy diver that needs to be looked after and forgets stuff, might run out of air, but is making an effort to correct the error of their ways.
3. Self reliant diver that has their act together 100% but still prefers to buddy/team dive. (Still the safest option).
4. Solo diver that is 100% self reliant (gear, skills, self bailout, etc.)