That’s why there is a feedback system there - as long as you look at the feedback (and actual comments listed) you can learn a lot about sellers before making a commitment.
I have been using Ebay for 5 years and have never had a severe problem with a seller. In all the transactions (over 60) I’ve only had 1 shipment that was lost and the seller quickly refunded our money. I occasionally get a slow shipper but that’s to be expected with any seller (on ebay or off).