Before buying the item?

I recently been scammed on eBay again; the package shows delivered but it did not, and the red flag is the sellers are using bot or copy and paste response. eBay and PayPal won't help me because it shows delivery, even though I never signed for it, they claim it was successful, as if packages never showed delivered before but never arrived. It feels like scammers have all the leverage, more and more. I called eBay out on their tactics, but of course, they did not reply.

PayPal didn't even look at what I had to say nor any evidence I posted, before, they used to rely on whoever posted the tracking number first in the report, which is also dumb, and they never get back to you and go over things a few times like any company should.
Amazon is much worse, as they employ a number of tactics, even preventing you from submitting your case, from wrong link, to pretending you never submitted anything if you're successful (hich you have to do some researching). Fortunately, I haven't had any mishaps for awhile on there.

Is there a way to know before buying if the sellers will scam or rip you off?
My advice, if you're buying a mobile phone, don't buy from eBay or Amazon. I bought 5 bad ones in a from flat out broken, to not as described. I finally bought it on NewEgg, no problem.