How to prevent applications from uncovering the technologies used on the website
Making all the Drupalisms disappear is hard work and most definitely not worth your while, as stated above by Clive. In addition, you'd also have to edit/obfuscate many of your http headers. 

At that point, if it were me visiting your site all the SSL and Trustee certs could not make up for trust lost and I'd leave. Plus, I might tell my nerd friends what a suspicious weird site you run and turn them off too. 

My advice: Don't break what makes the web work, and secure your site. You can and should stop nginx and PHP from advertising their version numbers, and you should delete Drupal's .txt files.