Real prop firms are not a scam. There's not that many of them (places like SMB) and usually hard to get into.
"Prop firms" in quotes are something between a Ponzi and a casino. Not really a scam because they are not banned and it's possible to get money out of them, however the people actually getting payouts is <1% of all traders and often it's the affiliates that promote them.
Another good point mentioned above is that an average retail trader has absolutely zero edge in scalping random forex trades. You can be profitable by swing trading stocks, finding edge in crypto. Some people can trade futures and if you like it more spicy, then stock options.
Forex is incredibly difficult, often random, all odds are stacked against you and that includes brokers and/or prop firms that will trade against you, add slippage and spreads or just completely fake the trades. Imho if a trader is long-term profitable trading forex at a "prop firm", it means he's in the 0.1 % and he'd be even more profitable if he switched to swing trading stocks with his own capital.