tomw, 
I think @dbushell is correct that modern #Wordpress, at least the way they want you to do it, is a "CSS-in-JSON-in-HTML-comments-in-a-PHP-file" mess.
Luckily you can just ignore full site editing and the not-quite-React nonsense and continue to happily write themes in PHP/HTML/CSS.
https://dbushell.com/2024/05/07/modern-wordpress-themes-yikes/