Why would you not add negative terms? Especially for shipping campaigns?!? That alone will reduce junk traffic immediately. Group your products by specific types or categories, it will help get you more relevant traffic, as well you can adjust the bids based on ROAS estimates, so you’re not bidding the same for a $7 product with slim margin as you are for a $60 one with more. Google Shopping campaigns can be like letting a drunk toddler build your keyword list