In real life yes, but its hardly unattainable in the game. True that it means the good ole grind is necessary to get it as it was with the other cars (And with still no repeatable event that doesn't require you to intentionally set up a slower car just to exploit the bonuses) , but its not like you can't get it.
“Hardly Unattainable” is extremely relative.
Each person has different priorities in the game, and different schedules.
How many Blue Moon races in a KTM does it take to earn 20mil? If a person has limited play time in a week, they have to make a choice - do I want to do sport mode, or online lobbies, or work on a livery, or work on a tune....or do I want to grind Blue Moon for credits? Keep in mind, majority of players who play GT know that those 20mil cars are useless outside of showing off in cruise lobbies. No one races them, if they’re in sport mode we’ll be given them for free....so what’s the incentive to actually get one, other than to say you have it?
Furthermore, once you get any of these 20mil cars, the default tune on them is complete junk, comes with the typical 60/90 damper setup (how generic can PD get???), so it’s not even anywhere close to a representation of what driving the real thing would be like. So you grind for X amount of hours to get nothing more than a 20mil skin that you can show off in a lobby (look how gud at teh game I are!!).
I grind 50+ hours a week, at my day job, so that when I get home, I can enjoy some virtual driving/racing, not so I can spend another X hours grinding for something that I payed money for.
Like I said before, if I want to drive a Mark IV GT40, or a Jag XJ220, or a Ferrari GTO, or a Ferrari 512, or a Porsche 917k, just to go for some hot laps to experience the car, I can do it right now in PCARS, with zero grinding - and it’ll be a more authentic experience on better circuits. Furthermore, I’ve put some effort into my life so that I don’t work for pennies per hour - meaning that the time it takes me to “grind the credits” in real life to buy PCARS along with GTS is a fraction of the time it would take for to grind the credits in GTS to be able to experience PD’s half arsed interpretation of a classic Le Mans car.
There’s no proper career in GTS, but at the same time certain cars are locked behind grind walls. It makes absolutely no sense as a game structure other than being beyond lazy at coming up with a format different from what we’ve seen over the last 15 years.
Even for someone who bought the game for sport mode to have to grind credits to be able to buy all the GT3 and GT4 cars that they’d like to use for online competition, it’s a complete waste of that person’s time.
Also just something else to keep in mind, and this is just my personal account, I just got the game a month ago. So, between getting up to speed in sport mode, completing campaign mode, sinking my teeth into the livery editor, photo mode, building my stable of highway cars with complete tunes, and enjoying online lobbies...when do I have time to grind close to 100 million credits to be able to afford the expensive cars? And what’s my motivation for doing so, other than to say, “look what I got”?