If WordPress is going to continue to grow, we need to think about what the long-term approach should be. I'd wager it'd be things like:

Continue the modular trend that Gutenberg started, eventually evolving into what is essentially modular components and a GraphQL API.
The above eventually evolves into provide WordPress in two flavors: 1) the ability to use only the components you want like the editor, user management, media, etc. for advanced use cases or 2) use the wholesale CMS like today.

This give the flexibility to use it as something other than a monolithic app while still serving those who do (most WordPress users). It's the same project, just more JAMstack-y so I can use what I need if I'm a developer building a more complex website or app.

This keeps WordPress relevant as websites becomes less relevant--every part of WordPress could be a best-in-class component. For example, why does every email newsletter app, website builder, business card maker, brochure designer, etc. have its own crappy editor implementation instead of using WordPress' Gutenberg component? This could be true for every other WordPress component. This would also greatly accelerate the number of contributors to WordPress. ...imagine the next new hot startup using the X and Y WordPress components and contributing back to them.

I'm not claiming the above implementation is right, but like Justin said we need a wider long-term vision of where we want to be, then work our way there refactoring piece by piece.