Keeping 3 separate native front ends in sync with custom visual components means you end up building a cross-platform UI. The only apps you can build without custom components are trivial ones.
Speaking of which, my dream is an "HTML light" standard with a subset of functionality specifically designed for local UI use, ideally with lightweight non-browser engines supporting this standard shipping with all major OS platforms as shared system components.
We had browsers that ran on systems with 8 MB RAM, after all, and while it's not a fair comparison, there's no technical reason why a system with three orders of magnitude more RAM should struggle to run more than a handful of applications merely because they use HTML and JavaScript for rendering.
Though 8 MB RAM is a non-starter when a single RGBA texture @4k is ~30Mb and modern system often require 2 or 3 for buffering. Somewhere around the 60MB to 100MB mark seems to be the base for modern setups, at least on macOS.
New rule: Programmers with limited UI experience (that includes myself) should abstain from weighing in on what UI designers and programmers need.