Is there something wrong (**SPOILERS**)

Nothing wrong with wanting them to end up together per se BUT

I believe their relationship was only meant to be for a limited time...like a one-chance deal. It wasn't meant to continue or to be a long relationship because the nature of their relationship was not authentic...meaning both Ben and Alexa were pretty much "using" Johnny for their own rebeliousness, sexual identity awakenings, and to do something risque at the end of their high-school life.

I don't think it would have been stronger because the true themes were revealed in the awkwardness of the three of them stumbling through their relationships.

I think the film-makers were trying to say something more profound for sure, but only in terms of one's identity (sexual or otherwise) and the reasoning behind it. Johnny obviously had a messed up family life and he had anxiety because of it and panic attacks. I feel like he really just needed to be comforted and needed the company of other people who treated him kindly. Both Ben and Alexa were truely taken aback at Johnnies suggestion near the end of the film when he said that they should all just start over again and do it right. I think they realized that Johnny had issues and truely seemed to "need" them both in ways they couldn't understand or appreciate.

Cause ben and whats her face are douchbags, and johhny is an emotional cripple.

To me it doesn't seem like a happy ending was at all possible. The other two are using Johnny for their own purposes, and it quickly becomes apparent they don't have a real emotional attachment to him. Johnny is so desperate for love that he doesn't see what they're doing. There are too many films with tacked on happy endings (see any Speilberg movie) - this one stayed true to itself and told a different story.