You've probably come across sites like this on the web, it has those annoying blurred overlays that require you to log-in/sign-up using a social account just to get to something you might or might not find useful. The example I've given here is Quora. So annoying these type of things have even been given a name - Dark Patterns.
Fear not, there is usually a way around this. Usually these blurred overlays are no more than a < div > in the page source code. Here's how to get around them...
Hit F12 on the keyboard. This will bring up the Page Insprector and the source code of the page. Scroll with your mouse pointer down all the lines of < div >s until you come to the one that highlights the blurred area or the log-in box. For Quora, below, you can see it's called '...signup_wrapper'.
Right-click and select 'Delete Node'.
It's usually that simple.