I think that Byler is the better story
At the end of the day, I just think that Byler will happen because it's the better story in my opinion.
Why go through, soon, 5 seasons with details about that Mike and Will has a more special friendship out of the core 4 group?
Why film and create the most beautiful scenes of heart to hearts between them if they're just friends?
Why create fights between them that feels more real, raw and emotional than Mikes fights with El?
Why (if they would not be endgame) make Will IN LOVE with Mike (SPOILERS) up until the last episode of part 1 of season 5? I mean, if his arc was all about accepting himself and that it didn't have anything in the end to do with Mike, why wasn't it resolved in, I don't know, season 4? Why drag it out? And the thoughts about Robin's speech being about/encouraging Will to get over Mike, I just don't see that being the case here because:
Mike is NOT Will's Tammy. Mike is not just a crush, he is Wills best friend, the one that lifts him up (sometimes literary) when he's down, the only one whose words really affect Will (as we saw in season 5 ep 4) in an emotional way, the one who has always believed in him and encouraged him even when Will didn't believe in himself. And the same can be said the other way around with how Will helps and always is there for Mike. I mean, it's because of Will in season 4 that we got leader Mike back in 5. And of course, Will LOVES Mike. And the video tape memories of Will accepting himself, including his first memories of Mike? It just shows that to accept himself he also have to accept his full love for Mike. I really like the theory about that El actually is Mike's Tammy which I really think applies well to their relationship. But the point is that the speech was not about "moving on" from someone that doesn't love you, it was about loving yourself and all parts that comes with that.
I've studied theatre, film theory and literary story courses - and it doesn't mean that I know it all (because I don't), but I recognize a lot of common storytelling mechanics when it comes to Byler from other stories than I do when looking at Mileven. Yes, Mileven has had some cute moments, but at the end of the day, according to me, I feel like Mike and El doesn't thrive in their relationship.
For example, they don't share the same interests, and that's not always necessary in a relationship, but in a series where DnD is SO IMPORTANT to the characters and their nerdy interest overall, I think it is. Because DnD is not just a hobby for the core 4, its a way to cope, a way to nurture their friendship with each other, a way to develop their creativity and strategic minds and a part of their personalities. DnD is important, being true to themselves is important, and I just don't feel like Mike is being true to himself with El, and the same goes for El. But With Mike and Will, I really do feel like they are being their best, genuine, selves: Byler is naturally nurturing each other while Mileven is trying to.
A lot of this has already been thought of and spoken about by others, and I agree with it all. I just really want to bring it up as well because I think that it's important to look at all the seasons, everything that Byler entails, all the signals and signs between them. And with all of this said, at the end of the day, after (soon) 5 seasons of a build up between Mike and Will, their story and their relationship just is the better story according to me, and I just don't understand how their story can end with them just being friends.
They are soulmates. And I stand by that.