Ebay, Amazon, Aliexpress - all suck from the technical point of view.
The ability to filter products, which is the most important thing in a webstore is almost non-existent on all 3.
Product titles are badly chosen on ebay, as well as descriptions and tech specs are bad and/or missing on Ebay and Amazon. They are better on Aliexpress probably because chinese spam all possible keywords in the title, and put a lot of pictures, but their search sucks.
I suspect it sucks on Amazon/ebay as well, but they do a better job in hiding it, so you are not even aware of the relevant products that are not listed.
Shopping cart awful on ebay, and pretty bad on Amazon too, mainly because you cannot select individual products from it.
Ratings completely useless on ebay, slightly useful on Amazon and Aliexpress because a few users are actually legit and post pics.
Categorization bad on ebay, worse on Aliexpress, non existent on Amazon.
Comparisons non-existent on ebay and Aliexpress, and a joke on Amazon.
You would think that companies that are worth hundreds of billion of $ would be able to hire capable programmers, or “engineers” or whatever they like call them.
Even the most basic open source ecommerce platform developed like 10 years ago has more features that these big ass companies provide on their websites.
On the other hand, some small stores do provide good user experience. I have seen a small hardware store with very good filters, categorization and comparisons, that would let you visualise several products from different brands from the category you would be interested at the same time. For example if I wanted to buy a saw blade, I could just filter by diameter, number of teeth, purpose and other properties and they would display a nice grid with all the specs form different brands for comparison. So you would actually end up buying the best suited product with good price-quality ratio