Good point. Indeed it is interesting to follow the Firefox Quantum approach (which breaks with XUL) or KDE's open source office suite, aka Calligra (https://www.calligra.org/) which is "plain C++/Qt" and thus not a sole effort to solve the cross-platform UI/object model problem such as Mozilla and StarOffice did in their time. Thanks to this, Calligra devs can probably concentrate much more on implementing features while getting a modern cross-plattform UI for free (literally: Qt is free).