Pretty convenient that all the insane time travel and Deke stuff happens when Fitz and Simmons are in a (relatively) stable relationship. It’s the future. Theoretically, they could’ve been sucked into the future earlier, they just weren’t.
Things might’ve been crazy in season 5, but imagine how much crazier it would’ve been if Fitz and Simmons met their grandson at the beginning of season 3. Simmons is still dealing with the aftermath of Maveth and her feelings for Will and she finds out she and Fitz have a literal grandson.
Imagine if they met him sometime in season 2, where Simmons isn’t even sure what she’s feeling about Fitz and all that he said at the bottom of the ocean, and everything is complicated and strange.
Imagine if Fitz and Simmons met Deke in season 1. Two best friends. One might have feelings for the other. They meet their grandson.