Went down this rabbit hole yesterday and played with LitElement/lit-html for the first time... great experience for folks who don't want much "ceremony". Was also SUPER impressed with AppRun.
The more that I depart from my "bare metal" web tooling the riskier/dumber things get. I always want to see a path back to a basic HTML5 shell, driven by almost-pure JS (w/tiny helper libs), and basic CSS. Just like basic UNIX tooling - basic web tooling just works!
To those thinking about trying lit-html; it IS as simple as the example on the GitHub project page. I was able to build it into a semi-complex application within a couple of hours and it had massive performance payoff w/o compromising how I want to build things. It definitely gets my "KISS" approval stamp.
You get a very React-like experience with components and functional templates in JS, but it's all standard JS, and there's no framework, just standard web components. The lock-in and risk is very low for enterprises.