i dont know why anyone was expecting a different kind of ending.
did you really expect marvel to spend years "rehabilitating" evil nazi captain america, did you really think marvel would even ALLOW an evil nazi captain america to remain part of the permanent canon of marvel?
hell the ENTIRE REASON this whole thing happened was the same way. a "living" cosmic cube made captain america young again and for whatever reason that altered his history and made him a nazi.
the whole story happened because of a cosmic cube, they end it with a cosmic cube.
its about the journey, not the ending.
this would be like someone complaining about peter parker becoming spider-man again after superior spider-man.
what the fuck did you think was going to happen?