Coulson, May, Daisy, Simmons, Mack, and Elena are stuck on a space station controlled by the Kree, and there’s no place to go, as the Earth has been utterly destroyed, and what is left of humanity is subservient to the Kree on board.
Rescuing Simmons from Maveth back in Season 3 practically seems simple in comparison to what they’re facing now.
The Season 5 premiere revealed that the majority of the agents were not simply transported into outer space as it seemed by the end of the fourth season finale.
A mysterious group on Earth abducted almost all of the good guys and sent them via monolith out of the atmosphere and the present day.