@GJS Nice compilation.
I'm no longer using Vivaldi at the moment, but that would certainly help me get back.
The fact that I don't feel my information is safely stored is part of it, bookmarks can't be faithfully saved/exported without information loss, and the fact that search engines are not safely stored in some well defined reliable and exportable way is troubling for me.
The lack of a proper portable mode is also a problem, and without thorough data export tools, exclusively relying on sync to properly backup and restore your data has been less than ideal, and failed too often