No, there are easier and more lightweight ways to create a cross-platform UI than to write HTML/CSS/JS: Tkinter, wxPython, PySide6, MiniGUI, Dear ImGui, Nuklear, React Native.
Having used most of those at lrast trivially. i'd have to say that HTML/CSS/JS abd frameworks on top of that are in par with the easiest of those for nontrivial cross-platform UIs, though the others may have other advantages.