note, I have never implemented search but suspect it's hard problem.

Still Amazon's search is pretty awful. I've found adding something in the category I want to my cart gets me better results than being on the item itself. In other words I might search for "wrench" and it shows me 50 items of which 2 are remotely close the the type of wrench I'm looking for. I click one, get new page for that product and below it shows other wrenches but they aren't remotely like the one the page is for. So I add it to my cart and suddenly it suggests a bunch of stuff that is actually close to what I wanted.

I also don't understand the pitching me things I already bought. I get pitching me disposables I already bought. I don't get pitching me a monitor or soldering iron or another mouse or keyboard. I'd think either via statistical analysis or via manual tagging they could figure out what items are more likely to be purchased again and not recommend another PS4 just after I bought a PS4? But who knows. It could be this is harder than it sounds or it could also be they suck at search or haven't gotten around to it yet or ...