I don't like the way eBay does certain things but I have no major issues with it. I bid what I'll pay - one time. If I get outbid or miss the reserve, so be it.
I bid on a car the other day & was outbid yesterday. I won't pay a nickel more so I've "lost" it. That's fine with me. I hadn't exceeded the reserve anyway. That's fine too - this car isn't worth any more than I bid - to me anyway.
At the same time, I've sold things for far more than I expected. Where I live, there's little market for much of this stuff so eBay gives me a worldwide market.
In my view, eBay - with all its problems - has transformed the classic car hobby like few other things have. I've been scrounging parts for these things since I was a kid and the change is enormous. In the sixties, I needed headlight covers for a Berkeley. I had to write to several places in England before I even got a response. The whole effort took about 4 months. Now, I find and buy similar things in a matter of minutes.
Meanwhile, I've sold a bunch of small Jaguar & Corvair (don't ask...) parts easily that I otherwise would have pitched. They weren't worth enough to advertise in Hemmings but were too good to throw out - & some guy in Florida now has some neat NOS stuff for his Jag restoration.
To some degree, the net itself provides all this, but I think eBay is a major player. I doubt that PayPal (another boon to car nuts) would have taken off as it did without eBay.
There is a downside, though. I think eBay has facilitated some large rises in parts & car prices, but that's another issue.