Not bad, but I couldn't find an Alola picture. *Ironic relevance joke here*

But seriously, these are her together because they are the victim of the same thing. If Misty was the original end game, and Serena was the update, does that mean May and Dawn missed out simply because of bad timing? The short answer is yes. It's entirely possible, given the same conditions, Dawn could have been written more like Serena was. May had no hope though, Misty was too relevant at the time. It's that simple, they came in at the wrong time. Gen 3 was around the time Game Freak realized they had a long-running franchise, and Gen 4 was riding on the current popularity. They weren't intended to be an end, the show would go on after, it was all but guaranteed.

As far as the interaction go, since some may argue there was a relationship between the characters, you have to remember: Kanto, Johto, Hoenn, and Sinnoh(wooo) were all based in Japan, whereas Unova and Alola are North America, and Kalos France. If you study the characters, you can see that they act like they are in the place their region is based on. It's perfectly logical for Serena to be romantic and fashionable, That's how we would assume someone from the Paris area to be like. May and Dawn are no different, they act like young, Japanese girls.

If you want some moments, go to bulbapedia.

Fine, here you go.

May seemed very fond of Ash, he was a nice guy. My favorite is her reluctance to let others join the group, seemingly to be alone with Ash. Who knows what 4kids did to her though.

The High Five. You know what I'm talking about. Secret handshakes are huge between best friends, but that only proves they are good friends. Psychologically, having one thing in common, or interacting differently for one person in comparison to others, makes two people grow very close. It still only goes for as best friends, definitively.

In conclusion, May and Dawn missed out. From a writing standpoint, it really didn't make sense to add a relationship for them with Ash, since he had his own journey.