I would pinpoint the time Ebay went off the rails to many years ago, when they changed their feedback system. The whole beauty of Ebay was that it was based on reputation. If I was selling something for thousands of dollars, I would only allow buyers that had plenty of good feedback. This simple system allowed you to avoid 99% of scammers. The only scammers that got through were people who spent a long time acting legit and building up lots of positive feedback, then "going rogue" and using that built-up goodwill to pull off a scam. This risk was small and worth taking (happened to me twice after hundreds of sales).
At some point, though, Ebay changed their feedback system so that sellers could not leave buyers negative feedback! You could only leave positive feedback, or refuse to leave feedback at all. Overnight, the entire reputation-based system of buyer/seller reputation was destroyed. Within three months of the change I was hit by three scammers, after selling less then ten total items. This was more scammers than I had to deal with in a decade of prior Ebay sales. There was simply no way for me to figure out which buyers were legit, and no way to warn other sellers which buyers were scammers. As evidenced in the article above, Ebay has absolutely no interest in blocking these scammers. Contacting Ebay inevitably results in a canned response that has nothing to do with your issue. Shortly after they changed their feedback system I stopped selling on Ebay all together. It just isn't worth dealing with the scammers, and Ebay seems to think that their current business model is fine.