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There is absolutely nothing “simple” about that. It sounds simple, but what does “someone has purchased a product” actually mean, in technical terms?
Let’s start basic, since this is a proposal about a federated system, there are instances. Who runs these and why? Does ever seller run an instance? can there be users/customers on those? if not, who runs the customer-instances? Who defines what a product is, and are products like communities? or more like posts? how do you correlate different sellers selling the same item, where a review would obviously apply to both? can you review a shop or seller? Are delivery services their own “entitty” and can you review those, too? When you purchase an item
Now without any answers to any of those question, let’s just go to the next level. Where are the reviews stored? in the instance where the item is sold (possibly owned by the shop)? or with the user? if it’s with the user, how does a webserver displaying an item find all the reviews for it? Does this differ between reviews for items and reviews of shops/sellers?
If a review is stored on the instance of the seller, he can just add an entry to the database stating “user x purchased item y”, and the review is valid. If the reviews are stored with the user, he can spin up an instance, and create a bunch of users there who can leave reviews, because he can mark sales as “valid” as the seller, no matter if there was any item and/or money exchanged.
I wrote all of this thinking about the classic sellers attempt at “creating good reviews to boost a product”, but there is the opposite threat of review-bombing (might be a competing product or seller, or you just don’t like pink shirts and decide to review-bomb those): How you protect against those has similarities, but reverses the roles essentially. Sellers are now the “target”, and reviewers the “threat”.
Aaaand this all is just about reviews, which have no monetary value. The platforms main goal would be to deal with physical items, exchanged for real money, and creating physical effects (like shipping). All those have to also be secured in a much more robust way. If a fake review or two slip through the cracks, who cares. But if just one valuable item goes missing (or is never shipped), or the payment for it, that’s immediately a problem.
Unless I misunderstood something, the PS5 isn’t “true 4k”, but uses upscaling just like any semi-modern GPU can do as well (DLSS and FSR I think is the AMD version). That changes that equation quite a bit.
I would argue that reocmmending a PC over a (new) console has gotten easier, especially for someone on a budget. Because you can actually get an incredibly competent machine these days (used of course). Even if you decide to pay more to get a better PC, you then have access to the vast PC library with all the bundles, frequent and often deep sales, giveaways, … The cost of the console isn’t just the console, but also what you can play on it and what it costs, and this aspect has improved massively on PC in recent years (and was already pretty good before then).
Of course, if you’re interested in exlusives or first-party titles (like nintendo), or you generally play mostly AAA games, the console might just be the better or only option, but you better bring the wallet for the whole journey.