For all its issues, I wouldn’t say iCloud syncing is one of them for Safari. I’ve had nothing but a good experience over the past couple years when it comes to syncing tabs, bookmarks and passwords.
There was a period where it sucked at syncing tabs for me, as it repeatedly showed tabs from other devices that no longer existed. Quitting them from that interface would not work as they would soon be back. I found many reports of the same problem online.
Fortunately it’s been working consistently well for long enough that I can rely on it again.