For those who have these requirements, you should try Mithril.js. It's small, robust, stable, has a strong community, and has been around since 2014. It's as close to plain JavaScript as you can get.
Mithril's flexibility is so well designed, we're still finding new and innovative ways to use it, even though the base library rarely changes. Having used React and other libraries for many years, Mithril is still the simplest and most pleasant library out there.
lichess uses it (mithril) for what is one of my absolute favourite examples of a truly well done web application - everything about lichess is just so well executed that if the author of a product like that chose mithril that's a strong indicator it's at least worth a good look.
Mithril's flexibility is so well designed, we're still finding new and innovative ways to use it, even though the base library rarely changes. Having used React and other libraries for many years, Mithril is still the simplest and most pleasant library out there.