I think if Ikuhara had stayed, Stars would at the very least have a more cohesive theme and still feel like Sailor Moon, rather than the phoned-in, hodgepodge mess of ideas it grabbed from the previous seasons but with little understanding on what actually made those ideas work. (See Usagi & Seiya's dynamic ripping off Classic's UsaMamo's, the Starlights antagonism mirroring the Outers but with a flimsy justification attached, etc) Say what you will about Ikuhara and his... eccentricism, but he at least always had a coherent vision and theme attached to each season he worked on. S was about the morality of sacrifices, SuperS about dreams and how that ties into growing up and what it means to be human, Stars is about.... pacifism? I guess? But that doesn't really come into play until the very last episode? Okay...
I disagree, I feel Stars had far more of a continuity problem than SuperS did. SuperS at least still had the supporting civilian cast in it (and even brought back Reika, who was a callback all the way from Classic!) meanwhile Stars nixed all of them, and even in the much lauded Nehellenia arc had Chibi-Usa & Hotaru act like they were little more than aquaintences despite them being best friends & Chibi-Usa being so broken up about her disappearance at the end of S.