The core of the issue seems to be that the Gutenberg editor is a way of editing content that is good for a specific use case but (very?) bad for other cases. If you run your own website/blog and have a need to 'design' your content in a more rich way than what's possible with the current editor, Gutenberg could be a very nice solution. Assuming the bugs and usability issues get fixed.

However, there are many cases where the Gutenberg editor is not the right solution. For example, for 95% of my clients for which I've build a website, the Gutenberg editor will be difficult to use and confusing. And it will make it almost impossible for me as the designer to control the design of the website if clients start laying out and designing every page themselves. It's already difficult to control with the current Wysiwyg editor (please don't create a pink text block if the brand color is red, etc).

The current editor (visual+text) is more of a compromise where a limited feature set is possible out of the box, while more features can be made possible from case to case (using specific plugins or functions in themes). It is a compromise, but works reasonable for most people.

That's why my conclusion is that Gutenberg should be a plugin or at least be an option to turn on or off per website by the developer.