You can refuse to take that "sealed game" and shop elsewhere. Every Gamestop I go to, when it's the last copy they let me know it is. Also if you think its not worth going to Gamestop in 2019 you're doing the whole cheapass thing wrong.
I know that and I gladly do. I indicated as well they tell you it's the display box copy and then they give it to you in an envelope and act like it's some impenetrable thing. I'm sure most of them are unplayed but I know a lot of people who have worked or do work there and I know for years they would bring home games and then sell them as new a week later. This was an allowed practice at the time, not people breaking rules.
Once again yes, every once in a while they have a sale where they have the best price for a week on one or two games, other than that they're beat in every way. Amazon/Walmart/BestBuy are cheaper for pre orders/day 1 games now if you're into that and Ebay/Amazon/game trading forums are almost always cheaper for used games period. So as a complete outlier yes, sometimes if you're lucky and looking for a specific game they might have the best price for that one game for a week but even then, the price can almost always be equaled or beaten somewhere online. I live less than half a mile from one so I go in relatively often and look around, if you go in and bring up Ebay/VGPC/Reddit and compare prices, it'll often be baffling and that's with their "membership discount." Also the rare $5-10 you might save almost isn't worth it after the 2-3 attempted up-sells you go through per transaction.