Are you claiming this is true about Inkscape? I agree with you on Openoffice/Libreoffice (although we disagree about the cause). But Inkscape has always struck me an exception.
If you are saying it has a bad UI, could you say more about what you tried to use it for, and what other vector-graphics program you've spent a lot of time in?
I always found Inkscape next to unusable compared with Corel Draw, Illustrator and Affinity Designer. Tried it several times, always gave up. In v0.92 (I know, not latest version) if I moved a point near the end of a path, points near the other end of the path suddenly started moving. Totally weird. I do not know how people can do serious work with this.
If you are saying it has a bad UI, could you say more about what you tried to use it for, and what other vector-graphics program you've spent a lot of time in?