Blah blah, Gutenberg whatever. It’s a great blog layout thing, I’m sure. I need websites for people that write content for other humans. A lot of people, and a lot of humans. Gutenberg doesn’t scale to that, and neither does TINYMCE, the WYSIWYG visual editor in WordPress.
I’ve always told folks to turn it off in their settings, but like I said, a lot of people, so I wanted to just shut it down. Turns out that is not apparent. But I tracked a decent approach, from Remove 'Visual' tab from TinyMCE editor - WordPress Development Stack Exchange.
add_filter( 'user_can_richedit' , '__return_false', 50 );
And done! Noting this, as this option is likely to never be addressed.