Agreed, I've had much more success with the horrors of .docx-compatability with OnlyOffice. It's not 100% perfect either, but has brought me less suffering overall. As much as I'd like to avoid Microsoft Office, depending on your situation that may unfortunately not always be so easy.
I'm not sure I follow, OnlyOffice is FOSS, buit has hosted solutions you can pay for, or you can download it for free to run as desktop apps or to self-host.