Every theme and every plugin you use on Wordpress is detectable if there's a reference to it in your page source.
https://winningwp.com/how-to-tell-wh...-website-uses/
You can't block most of these sites as they use common search engines to find Wordpress blogs - you'd have to block the originating crawlers - so to resolve this you could just put the following in your robots.txt file
Code:
User-agent: *
Disallow: /
Then say goodbye to any search engine listings as well
