[dmitriid]

Riight. What you're saying is: "we must have horrible imperative code that takes three times as much code as a simple declarative/fluent API because ... reasons".

There's next to zero requirements for "static get observableAttributes" and "attributeChangedCalback" which in 99% of the cases can easily be replaced with

   static get properties() {
       return {
         x: {reflectToAttribute: true}
       }
   }

etc.