Is it possible to preserve Islamic brotherhood long-term without a prophet?

Assalamu Alaikum. Lately I've been hard on myself for not doing more to help the Ummah. I catch myself thinking: why can't I overthrow the West and bring every land under tawhid, end all ikhtilaf among Muslims? In theory it feels like something that should be done, but in practice it's beyond me - and maybe it's not my role to try. Perhaps that's something only Allah wills to happen, and maybe a change like that would come with the return of Isa (AS), not by our hands. We already saw the Ummah start to fracture after the Prophet ﷺ passed. His hadith about divisions after him seems to reflect reality. Even when Isa (AS) returns and rules for forty years, the narrations say fitnah will reappear afterward. Sometimes even prophets couldn't stop division: the Children of Israel remained split and disobedient despite many prophets being sent to them. I can't find a historical example where Muslims stayed fully united and obedient for a long stretch without a living prophet and without innovations or fitnah. So I'm asking: what would it take for the Ummah to maintain that unity and fidelity over time? I don't have a model to follow, so for me it's a mostly theoretical question. It seems religion tends to erode and people tend to vie for authority when there's no prophet. Right after the Prophet ﷺ left this world we had the Ridda and claimants with false revelations. JazakAllah khair for any thoughts or reflections.