I generally just roll the dice with Amazon on anything that is not food or electronics. The convenience trumps the money wasted on buying a bad product.
For electronics, I've looked at Walmart and Jet.com which have shady 3rd party sellers that are worse than Amazon sellers.
I believe BestBuy gets all its inventory from authorized sellers so I trust them, although they have limited selection.
I haven't found a solution for food (mainly specific branded supplements like magnesium/vitamin C/etc. that can't be found in regular grocery stores)
The ideal situation would be if Amazon didn't conmingle its "Sold by Amazon.com" inventory with 3rd party sellers and charged a premium for it (to make it economically feasible for them). Right now the current incentives aren't pointing in that direction.
Most customers don't know about the conmingling. If we could spread awareness of conmingling, the economic incentives could lean in that direction.