Just read this quote
Commenting on the next-gen versions of GTA V in March, the CEO of Rockstar parent company Take-Two said he was confident the remaster would deliver a strong experience for players.
“We’ve done great with the Mafia series, for example, and Grand Theft Auto [V] is now heading into its third generation which is incredible”, said Strauss Zelnick.
“It was a standard-bearer when it was launched, it continued to be the standard-bearer in the second generation, we’ll see how Grand Theft Auto does in the next generation. Obviously, I’m confident that Rockstar is going to deliver just a great experience, but you can’t do that if you’re just doing a simple port.”
Differences those Mafia games are older and got rebuilt completely this clearly has not and its a port of PS3 game from PS4 to PS5. Modders have added more to GTA 5 since its release and done major overhauls of the entire game scenery weather cars etc