Association/MyGM comprise about 99% of my NBA 2K experience and have for years and years.
I wouldn't exactly say the two modes are drastically different. The overall objective is the same. But I think 2K looked at Association Mode and tried to fix things that didn't need to be "fixed" while ignoring (or maybe not seeing) the things that would truly add to the realism aspect so many (including myself) are begging for.
Having discussions with my owner is kind of fun for about an hour. Until you realize just how mechanical and forced (and in so many ways, unrealistic) it is. I just don't need 10,000 unnecessary cut-scenes per season of coaches and Assistant GM's and owners and the arena janitor telling me every detail of their day-to-day life and problems. But I also don't want to ignore it because then I get penalized.
Then you take into account VC which shouldn't have nearly as much of a place in Association/MyGM as it currently does. Having to pay VC to set your damn lineups? Really? I mean......seriously? Like, for-real?
The things that truly add realism to a team-building, dynasty-building mode are things you'd hope to see if you truly owned a team long-term (duh). I'd want to have the ability to build a new arena from a list of pre-constructed options. I'd want to be able to edit the team's name or jersey (or both). I'd want to not just see the HOF retirees' names on a boring-as-heck board but see their jersey possibly hanging in the rafters (how amazing would a jersey retirement ceremony be, even if it's as short as the cutscenes where the Championship winners receive their rings?) and be able to see their statistics, accomplishments and All-time rankings. Having draft reports throughout the season leading up to the draft would add to the excitement of reaching the off-season, especially if you're a rebuilding team with a top pick. Adding a weekly-wrapup segment ala NFL 2K5 and Chris Berman would keep you up to date with the goings on in the league (Sorry but the NBA.com thing is really slow and, again, incredibly repetitive). When you're doing an Association, it shouldn't be ALL about YOUR team. You should actually care about the other teams and their state in the league as well.
Things like these really immerse you in the experience. And more importantly, they have replay value. Even I, one of the most dedicated Association/MyGM players there are in existence, haven't been able to create more than a few teams and take them far at all before the monotony of the mode reared it's ugly head.
Even if the developers decide to implement none of these things, at least make the CPU-created draft classes and simulated statistics more realistic. It bares repeating for yet another year in a row that not all drafted players are incredibly well-rounded. Just because you're a good player doesn't always mean you're going to put up 20-5-5. Sometimes, you're a really good point guard who likes to pass the ball (GASP!) and average 15 and 10. Maybe you're a dominant rebounder who can't pass the ball for anything (a 18/13 guy who barely gets 0.5 assists per game).
Have more pre-set faces so I don't see the same 15-20 faces (with different hair and beard styles) every draft. Make sure most of the players are hard-wired to NOT have ridiculous haircuts, tattoos or accessories.
Sorry for the long rant and there's so much more I could say on the topic but I've probably gone so far off the purpose of this thread that no one has even read up to this point!