My prediction... AI will never work for shopping.
I reason this because no store will ever make an AI the users will ever want to use. Stores will always try and push what works for them - not what works for the customer. Taking a simple example, lets say I need to buy some AA batteries. The vendor will always try and push me to whatever makes them the most money or empties their warehouse the quickest, so they'll sell me a big box of batteries, or they'll sell me premium brands, or they'll sell their own brand and try to hype them as being as good as the premium ones - whatever works best for them. Whereas, I would like to buy a smallish pack (so I don't have to spend so much money, and so they don't "go off"), I'm not really bothered by the brand, so long as they actually work well and keep their charge for a long time. Once I've figured that out, I'm price sensitive, so I'll buy the cheapest of the "good looking" ones - whatever any of that means, I'll compare deliver times/costs, etc. Either way, it's almost certainly not in the vendors best interest.
Could a third party (eg. a comparison website) make an AI that works for customers? I suspect probably not for all the same reasons as above. Ultimately, the aggregator relies on the vendor, and the vendor will be pushing their own agenda, so the aggregator will be tainted by that too. The aggregator needs to make money, and so they'll introduce (or persist) biases just like the vendors do.
Could an open source option surface? Maybe, but it'll be beholden to vendor data, so would probably struggle like the aggregators would.
Aside from the obvious vendor biases, I suspect the buying decision is also actually insanely complex - I'm wondering if it might be a problem like self-driving cars - it looks simple on the outside, but it proves to be really, really difficult to get right. If you've ever seen someone pick an apple at the supermarket, you'll know that some people seem to have a lot of unpublished, and largely irrational variables in their buying decisions. Getting all of that right seems like it'll be very, very hard.