I'm 100% on board with used games. Get a game I want at a cheaper price, which means I save money towards any future purposes I wish to make.Always a win for me. But I can see the issues people have with it based off the type of quality a disc or game might be in. Just depends on where you buy from I suppose.
Yeah I've seen a few people have issues over this sort of thing but places here in Ireland and the UK have CEX who offer a guarantee that the goods you buy from them will work and offer very long cover on second hand consoles and other electronics.
You could also look at it from another point of view, if you buy a used game you are technically recycling something which another person has no use with anymore, what would the alternate be if used games market didn't exist? For them to either leave the item on a shelf forever or else to landfill it, the system in place now means that gamer can get rid of the item in a way that they get some cash back towards what they'll likely spend on another new game (as many stores off more store credit than cash for games) so the cash one person doesn't spend on a new game by buying it used actually still part way funds the sale of another new title as well as takes care of a recycling job (in a way)
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8