Same with France, also applies to warranty, or delivery issue, or... You buy from X you deal with X.
Not only is it much better for the customer, it's also clearly profitable.
It can also act as a differentiator, many retailers here including some big French ones tried to play around that law with the marketplace system, "we are not the seller just an intermediary", and while changes to the law is on its way to stop that it allowed Amazon to easily take over by not making that distinction.
There is still some issue about the difference between shipped by Amazon or not for the warranty request (not refund or fake or... but regular warranty issue), which I hope the law tackles head on.
The one time I had a problem with an Amazon item it was immediately refunded.
They are still operating in the UK so can clearly operate profitable under these rules. You shouldn't accept anything less.