Hi, builtwith.com caches the results and hence might be showing the result from cache. And regarding isitwp.com detecting wordpress, I can still see some text/comments added by plugins in the source code which reveals it as WP site. Please remove/replace such text/comments using “replace in html” option under replace tools tab.
If it’s still being detected then please let us know your website’s wp-admin login details (as private reply), so that we can look into it further.