Brehh... Ratchet is not seen as a "shooter" like any other TPS game. It's also not that open, the levels are fairly straightforward.You mean the game that is 90% shooting with loads of open areas
To say it sold and was rated high because it was openish with shooter gameplay is silly as that would mean Knack would've been rated highly as it had open areas and it was more of a brawler. A good game will sell. It doesn't have to check off modern day game tropes to be received well.