You're wrong.
I know very well the kind of rendering features and techniques that make up for the look of a next-gen game, a last-gen game, and each generation before that, as well as the particularities of Rockstar's internal technology. So excuse me, but I'm way more educated than the average user that throws the "cross-gen" tag at every single new game release that hits the market.
Apart from that, I come from literally playing a pristine-looking next-gen open-world game at native 4K, maxed out settings and with RT in Suicide Squad... and the elements that are not blurred out by the compression of this latest GTA VI look several steps above that. So yeah, Grand Theft Auto VI definitely doesn't look fucking cross-gen in this performance mode 1440p footage.