HTML & CSS themselves have become a major bottleneck to quality and creativity. The arcane layout model, the baggage of backwards compatibility, the cognitive dissonance — played out over decades of design-by-committee — between "this is a document engine" and "this is an app engine."
The rendering-thread-is-the-main-thread architecture of JS plus the JS garbage collector cause jitters & frame drops that most people don't consciously recognize, but everyone subconsciously recognizes. These little bits of jank are why consumers can recognize webview-wrapped apps vs. native apps.
Don't get me wrong — HTML and CSS and JS have brought us far, and the zero-trust execution environment that is the browser is an amazing feat of humanity.
I hope the "new ways of doing things" you describe include a major innovation on HTML and CSS and JS. WebAssembly makes this possible today — and I have dedicated the last few years of my life to proving this concept[0], and I hope others explore similar avenues. We deserve a better substrate, and this can be done without reinventing the browser.
[0] www.pax.dev