So Paps rated well below is even less special. Anyway. who really cares about kick return metres. You want your fullback to be participating in sweeping backline moves. Kick return metres are for props and wingers.
I'm not sure why you are hung up on Paps? I'm not saying 13th is nothing special therefore Bula is shit. Just that 13th for kick return metres is nothing special. No one should be saying look how awesome Bula is he because he is ranked 13th, which someone did.
I pretty much agree that Kick return metres shouldn't really matter. For a team it should matter but less so for an individual. It is specifically about what any one individual brings to the team and the team dynamics ensuring those strengths are utilised. Some fullbacks kick return metres is one of the main strengths they do bring (Edwards, CNK).
For most, as you say, it is what they bring to backline moves that is their strength. This is where Paps thrives with his speed creating indecision in defence and turning half chances into clean breaks. Similarly Trbojevic and Mitchell's power running sees them either trample defenders or suck enough in to free up the outside men. Others don't have the same running strengths but elite pass selection Boyd was excellent, Gutherson is pretty good.
Most good fullbacks have more than one attacking string to their bow running metres, speed, power, pass selection, support play, even a kicking game.
In defence people talk about their ability (or usually their inability) to clean up opposition breaks. The other trait that doesn't get spoken about enough is how well the fullback organises a defensive line.
Now I originally said I think Bula is somewhat over rated (which is why I think you keep mentioning Paps). This has nothing to do with him "only" being ranked 13th. As I've said multiple times his kick return metres is fine. I think he is over rated because I don't see any one facet he is particularly good. Now to be fair he is pretty good at most aspects of attack ( and a great cover defender but can't organise a defensive line at all). He just isn't exceptional at any one thing. Yes, he is young and can still refine his skills but I don't see him ever being elite. I think his ceiling is a Will Kennedy. Fine player not the elite fullback that I keep reading Bula is/will be.