v1.5 seems to have a bunch of bug fixes and deprecation (Hah! I'm not sure if it's like move fast and break thing). It is potentially the case.
In every important part, there seems to have a solo smart person working on it. E.g. Cowboy(I know it's erlang but Phoenix depends on it significantly), Distillery. That could be a good thing. Less people may catch up with each other faster. It also mean a load of works! And also mean some convention are out of sync (e.g. configuration which I think Conform is the proper way lately)