Glad to know others have had the same experience. (Misery loves company?) I notice things often DO sync quickly, so I think “Hooray, problem’s solved!” but then it’s not.FWIW I've always had problems with iCloud tabs, for years, to the point that I have disabled them and pretend the feature does not exist.
But bookmarks and reading list syncing have always been perfect for me -- until recently. Now they don't update, or they appear in wrong order.
I have also tried many things to fix. For now I have given up and will try to live with it.
It is very disappointing.
Think I’ll give up trying to fix it, too, and just live with it.