> I have often had a look at Google shopping results but very rarely clicked one.

Pretty sure that tab is all ads, so its all garbage, in some cases some of the results look like scams.

It worked great for me recently buying running shoes.

I knew what shoes I wanted, there are plenty of no-name merchants selling them, competing on price (last year's model, so not being sold in big name stores). Click through each of them, find one with the right size, colour, delivery prices. Very painless. If some of the merchants are scams, I wouldn't know, my shoes arrived anyway.

Instead of "all ads, so it's all garbage" this is exactly what I wish all advertising could be.

It's not all ads. Indeed it's mostly not.