I tried OnlyOffice once and couldn't stand it. It felt as horrible as MS Office. I'm a happy Libreoffice user, and find that their UX choices make sense once you look into the rationale and are very functional and easy to adapt to.
I guess everyone's experience is different, but I'm always very surprised and humbled when people talk passionately about how bad the UX is on projects, which I use because of their UX rather than despite it. (GIMP is the other big example here)