It is really hard to fake Ebay reviews, because you can only leave a review when you buy or sell a product. Unless the seller macros selling and buying $1 pen or something similar, it’s not possible to leave many fake reviews.
So, go and check their reviews and see if they are a regular seller of shoes or boots, or any products that you want to buy from them. If the seller has a lot of reviews of related products, it’s usually a good sign.
I would not mind one or two bad reviews, because we can all make mistakes. Sometimes, you will be late to the post office, sometimes you are too busy and sometimes you don’t know where the product is. However, I would pass on the seller with many bad reviews. It shows that the seller is not genuine or even a scammer. If it’s consistent, it’s not a mistake.