Are EU cookie consent forms safe?

It increases dialog box fatigue. By overflowing the user with mundane dialog boxes, they are more likely to get into the habit of just clicking OK to remove the dialog box from their screen. This increases the risk of a user clicking OK on some important security decision presented in a dialog window.

This form effectively gave all websites a valid excuse to interfere with browsing until the user clicks on something.

This is indeed a bad thing: browsers have gone a long way protecting the user from malicious websites by limiting the actions that can be performed without clicking (like blocking pop-ups which are not a response to a click). Once the users will learn to click on anything which blocks the view and reads 'cookies', those defences won't help much.

So, apart from the increased risk of clicking the wrong button, there's also a risk of clicking a button on a site where all buttons are wrong to click on.