How to detect technology used in web app?

By using wappalyzer chrome extension, we can detect technologies used on the main page.

But few of the websites like google, facebook, Gmail and Amazon,... won't show up any technologies. Does it mean that they are not using any frontend frameworks or technologies? Or they have their own? In that case, till sometime back facebook was showing React. Now it stopped showing? Are they doing any sort of technical hack to hide the technologies from outsiders?

Is there any other better extension which provides such details? Would love to hear your inputs on this in detail.

For security reasons, if we can also do the same thing, what are the measures to be considered?