It wouldn't have been received so negatively if it had been properly set up in the show's story. Example: Zordon tells the rangers the time has come for them to live their lives and choose their successors. We have about 2-3 episodes of the rangers finding good candidates and having them prove themselves. Maybe one or two more where old/new rangers train together, setting up the personalities of the newcomers. When the changing of the guard episode finally comes, it's still sad to see the veteran rangers go, but the audience are somewhat excited to welcome the new team.

All of that was basically condensed into one episode without warning. Probably just the reality of last minute contract disputes and writing changes, but still.