Speaking as a website owner, I basically do this already. Preferring to use Elementor for pages and Gutenberg for posts and others.

Speaking as a plugin developer, I think this would be very welcome by developers. Creating proper support and standards for plugin companies to create unique editors that all play nicely with WordPress would be great. Then natively giving the site admin the choice of which editor to load for which post type, of course with Gutenberg leading the way as the default editor out of the box with WordPress when you install.

I’m all for it and I think a lot of others would be too. It’s very much in the spirit of WordPress.