White spaces in HTML trick many into writing complex CSS — web development is trollish that way. Firefox’s developer tools show generated white spaces! Hopefully your abstraction is munging HTML faithfully. It’s easy to fight white spaces without realising it. That generally leads to using unsuitable display types and other shenanigans.

Take the innocent PHP web server cli.

php -S 127.0.0.1:8080

Best not to use PHP’s web server cli (even for PHP) because routes with a dot (.) are assumed to be static files. Use a real web server or superior cli web servers with minor gotchas.

python -m http.server --bind 127.0.0.1 8080
busybox httpd -f -p 127.0.0.1:8080
ruby -run -e httpd . -p 8080

might try out the Fresh framework from deno to see if the hype is true hype.

Reading about the Fresh framework lead me to an article about islands architecture and progressive hydration. “Island based client hydration” looks like a type of progressive enhancement.

Wonder how an adjustment to that theory pans out? Might be enough of a golden hammer for most use cases but imo, scaling/speed issues are more fundamental/situational. You could swap between or hybridize client/server all you want and still mess up.