Too many scripts from too many places
Running uBlock, or similar, seems like good idea. The problem is that many eCommerce sites have scripts running from so many locations, you can't tell which ones are irrelevant crap, and which are necessary for the purchase to proceed. So you end up inching through the purchase, playing guess the script, enabling each one in turn. All the time hoping that your purchase doesn't disappear with the next page reload, or end up debiting your credit card twice.
Online retail sites need to get it through to their thick heads that I have never, ever, found the need to relay news of my online purchases to some social media account. And I am not interested in being tracked by anyone while I am on a page entering my credit card details. For any reason.
At the point of purchase that is all I want to do; purchase. The only people involved in that exchange should be me, the website I'm on, and the relevant bank. That is all.