It's not about my headcanon, it's about how they wrote the story. You think it's just a bad writing decision and they shouldn't have done it, but I think it was a great writing decision, depending on how they end it. They had Will claim his painting is from Eleven, his feelings are from Eleven, and convince Mike that Eleven needs him. They wanted to make the viewer empathize for Will and want for Mike to realize the truth. He never found out that Will was talking about himself. So the logical ending is that Mike is going to find out the truth and then we find out if it's unrequited or not. Maybe in the future he will realize he loves Will back. But there is nothing wrong with people wanting Wills love to be requited, the show seems to encourage it by writing him in love with Mike. Only certain fans seem offended by this. Not everyone likes Mike and Eleven as a couple or agrees that Eleven needs to be in relationship with him to be happy. I think the most important thing for Eleven is to be free from the military project and have a normal place to live and get her real mother back.