Why does anyone like Simmons and why does Fitz even like her anymore at this point?
1. He nearly gets himself killed saving her life when Grant tries to kill them, Simmons does nothing to reciprocate Fitz feelings
2. Fitz has a mental issue for most of the next season and Simmons leaves to take on a mission without ever reciprocating Fitz feelings
3. Finally, when Simmons does start reciprocating his feelings, she gets sucked into a portal and transported - I'll give her a bit leeway on this
4. She spends months on this planet, still holding on to those feelings, when Fitz has been trying to get her to come around for years, only to completely flip around in one moment of despair
5. Fitz saves her life and all she can think is, "I gotta get Will back!" - I'll give her the benefit of the doubt for right now that she's doing it purely to save him because they kept each other in check, and not because that a mere month or two of having feelings for this guy suddenly supersedes years of courting by Fitz.
I don't like Simmons all that much, and I hate, hate, HATE, love triangles. Worse romantic plot devices ever.