I think Marvel's main hang up is that while Marvel is technically trying to get over on Sony, they are still doing them a HUGE favor by taking creative control. But Sony want to be play like they are in the power position on this deal and be able to use Marvel characters in Sony produced Spidey movies w/o Marvel's permission... and that is certainly a deal breaker, because that means more contract negotations and possible interference w/ ongoing MCU plotlines and characters.
Sony just needs to realize that they get to profit from Marvel doing most of the heavy lifting and just accept that check. Almost no risk, all reward. and they no longer need to waste time, talent and money on terrible movies that should've been good.
One thing I do want to know, is what does this mean for Drew Goddard? Who left his passion project of Daredevil to pursue a blockbuster writing/directing role for Sinister Six?