There are a number of very good page builders for WordPress. These builders have evolved over time, with a ton of user feedback.

They are successful because they do a good job and allow developers to build sites quickly, the way they want.

I don't entirely understand why WordPress core is choosing a completely different approach, without even considering to use/build something like developers show they want.

A few years ago, WordPress adopted the menu system from WooThemes, which is now our standard WordPress menu. Why not do the same for the editor?

I'm pretty sure that all the developers of the popular page builders would go out of their way to support the WordPress core in including/rebuilding a new editor.