That's, er, not actually true. The casino in GTA Online operates entirely with its own currency, which is given out in small amounts for free daily, or can be converted from the normal game currency (and back again). In theory, players could buy the game currency with real money and convert it to the casino currency, but I think there's a daily limit too. There's also no content locked behind the casino games, they're just the standard basic games that pay out the casino currency. As far as I'm aware, most of the regional blocks were in countries where electronic gambling is illegal or heavily regulated, regardless of whether real money is involved, or where allowing children to gamble is restricted.
Other than the content exclusive to the PS5 / XS versions requiring that version of the game to be bought, I can't think of anything in GTAO that forces a player to spend real money. I've played it casually for years and it's never cost me a penny, and I've been through all of the expansions and available missions over that time. Contrast that to FH5, where the car pass is a real money purchase, so is the Hot Wheels expansion, and two cars are locked behind partner purchases (the '32 Ford FE and the nail polish Ford GT).
I'd also say that GTAO is actually a great example of a GaaS model extending the life of a game, as there's absolutely zero chance that GTA5 would have still been getting new content and missions for free 9 years after launch otherwise.
