The whole 'Adelaide has a player retention problem' argument is a bit of a myth as far as I'm concerned. The only reason it's even a point of discussion is because of the quality (not quantity) of the few players who have left.
Bock
Davis
Tippett
Gunston
That's 4 players in 5 years, 3 of which have gone on to provide appalling value (mostly due to injuries) for their new clubs. During this same period, the club has picked up Sam Jacobs, Eddie Betts, Josh Jenkins, Luke Brown and Tom Lynch (to name a few) for absolutely nothing of any significance via trading and free agency - if a couple of the blokes who left had stayed, not all of these moves would have even been considered. All have provided fantastic value for Adelaide and are now all in the best 18 without question (I'd argue that all 5 of them are in our best 12-14). Not the end of the world if you ask me. There's also been some handy drafting done in this time but that's a separate issue.
I'm pretty sure most clubs would have a comparative list of players who have departed, despite being 'required players' over the last 5 years or so. Many would exceed it. Player movement is part and parcel of today's AFL, and the only club that should really be alarmed is Brisbane, although I suspect Essendon and Carlton might be feeling the pinch soon too (if they aren't already).
Adelaide's (and Port Adelaide's) main hurdle is always going to be geography. Some 20 something males find Adelaide the city a bit dull, especially ones who grew up in bigger cities. Shit happens. And in some cases, regardless of geography, money talks. Tippett, Bock and Davis are all examples of blokes being offered deals they essentially 'couldn't refuse', but that certainly isn't an issue that only affects the Adelaide footy club. Tom Scully, Tom Boyd, Levi Greenwood, Eddie Betts (arguably other factors at play), Mitch Clark (when he left Brisbane), Nick Malceski, Gary Ablett, Shane Mumford (when he left Sydney), Dale Thomas, Lance Franklin, Brendon Goddard, Danyle Pearce, Rhys Palmer and Troy Chaplin are all relatively recent examples of blokes who have shifted clubs predominantly for a big payday that their previous clubs simply couldn't / didn't want to match. I don't really think there's much these clubs could have done to prevent these guys departing in terms of culture, environment etc, and Tippett, Bock and Davis all certainly fall into this category.
The only player from Adelaide who doesn't fall into the above category is Gunston. Supposedly he was just a depressed, homesick 20 odd year old. Was he depressed / homesick / wanting to leave the AFC because of anything other than geographical factors? I've never heard anything to suggest he was but you'd have to ask him.
As for Dangerfield, it's a very similar situation to those faced by Dayne Beams and Travis Boak in recent years. The lure of home vs loyalty to the current club. Beams left, Boak stayed. Was Beams leaving a poor reflection on Collingwood as a club? I didn't really think so, no.