Some ideas. . . .
Don’t argue about things that don’t exist, like whether Save buttons should do this or that. Instead, code or prototype it and then team members use it themselves. You’ll be able to tell if it could be better when you use it instead of talk about it. . . .
One of the biggest blockers to team greatness is that members of team will have really good team diagnoses but they don’t say them out loud. So nothing can be done with the idea. You gotta say your great ideas out loud. . . .
Stay out of the content. The real issues are not about UI and architecture. Those are just the excuses to act out team neuroses. . . . If you resolve the interpersonal issues you won’t feel like you have UI or architecture issues.
Processes and planning will not make this better. They will make it worse. Don’t have a meeting to discuss how you will do the UI, for instance. That’s one of the worst things you can do. Don’t talk about stuff that doesn’t exist. Make stuff and then perfect it.