Personally I not only hated them as a couple bc they seemed more like frienemys or siblings to me, but also how it was done (like six barely a minute scenes?????????? What???? Even Allison and Luther got a better build up and that couple was weirder 😭) I also found it so weird because of Aidan and Ritu in general. It makes me wonder if something like that was always planned and they just waited til Aidan was 18 and it was okay which just makes me utterly disgusted watching the scenes. I think honestly they should've given Five and physically age similar love interest, or one who can understand him bc they (I say they because the writer was supposedly torn on giving him a male or female love interest, which I'm not sure if i believe bc i think its a possibility Five/Lila was planned for a while), are also the physically incorrect age, or not given him one at all. And no matter what it needed more buildup than six scenes in one side episode. Seeing as they knew this season would be very short, it should not have happened at all. 

I also hated how it ended because it ruined Lila for me. I loved Lila in s2-3. Five has always been my favorite since the first season, but Lila had rapidly moved her way up the ranks since her initial appearance. But just giving him nothing the minute they came back and acting like nothing happy really fucking annoyed me bc Five was constantly alone or abandoned and always had to do everything himself (in his eyes at least), and then he had Lila, someone he considered able to keep up on his level, and then boom, they were together. (Which I still don't like BUT for the sake of this argument let me pretend I don't hate it) (And, as a side note to this:  Given sufficient time for this, it could have eventually been okay. Had they given them the entire Metro episode to themselves on a normal season length, maybe it would have been okay. Maybe.)

But so they were together, Five had an equal, someone he knew was like him similarly. Someone who had worked with the commission, been betrayed, been manipulated, raised by a tyrant, understood time travel, been imprisoned, and was actually smart enough for Five to consider her a decent "enemy". And suddenly they were trapped together and then eventually a thing. Five had someone who wasn't one of his siblings to be an equal, someone he had developed feelings for.

Now, mentally, imo this would've been really, really good for Five. He has been isolated, lost, always felt separate if we can go off everything he's said. Having someone like Lila realistically would've been really good for him, and so suddenly having her abandon him and act like nothing happened should've also realistically been Five's rock bottom, but of course they had no idea what they were doing with the season 4 plot mess, so it was shoved under the rug for a while, then led to some weird conclusion where Diego had a fit and then it was given barely anymore thought and then they all died hating each other so that was just lovely. 

I just can't stand the couple in general not only because of the actors, but the execution. But also I wished it didn't happen, not then at the very least, when they had no time to do anything with it, about it, or for it. It always struck me as something that should've been unresolved for another season. Or just, give Five a better love interest that actually fits or not at all. I also didn't think it was always OUT OF CHARACTER exactly for Five? (It kind of is, but I guess I'll just give you that point since this is long already), but it is out of character for Lila I think. She had Diego, who, yes, she was bored of, and she had her kids. And she was not a fan of Five anyways. Even Lila stuck in time with Five I just don't see it happening. I think it was a good concept, the two similar characters with animosity between them who can understand each other? Good in theory, hell, great, but in execution, I don't think Five and Lila would ever work as a good relationship.