Weird, because we're using web components at my workplace to build complex web applications. We use Lit-Element as a base class and have come up with a top-down functional state pattern for data that removes the need for two-way binding. If a sub-component needs to update its state due to DOM interaction, it just fires off an event with info about that DOM interaction, and the data store for that component (another web component) does the necessary state modification, then fires off a "state-changed" event that tells all associated components to update their state from the "master" store (one line of code). All of the data elements use pure functions to do state modification, so doing complex operations is simply a matter of composing the appropriate functions. I've not used react myself other than playing with a few demos, but another developer on my team says the pattern is very similar to how react stores work, and the core modules that drive it are like 100 lines of code.