1st class is 18h of extreme comfort. Starship would be a few hours of extreme discomfort. It's very likely much of the target audience wouldn't even survive the accelerations if they were allowed to attempt it.
It's 60 minutes to any point on the planet. 100 people fitting comfortably with a lot more room than a current airliner. The G forces are meant for humans. Very different considerations. No need to bring food or have bathrooms when the flight is that quick.
The G forces are meant for astronauts, not for regular people rich enough to buy this flight. And the whole point of first class is that you pay for luxury. The duration of the flight barely matters, the luxury is the point, and a rocket just can't offer that. There are very few situations where rich people would be willing to put up with the discomfort for a shorter trip.
Especially given that the total trip time will likely be much longer than the flight itself. Consider that you can't take off or land Starship anywhere near a densely populated area, it has to be at least a few hours away by car from anywhere that people actually live.
So you can take a chauffeur to the airport, go trough priority and special luxuries as a first class passenger until your flight for say 1h total, board your 15h flight spent in luxury, and then a limo waits to take you to your destination 30m away from the landing airport.
Or, you can get driven for 3 hours out to the Starship launch site, board the rocket, probably in a special life support suit, wait some hours on the ship for it to be filled (humans are never allowed to approach an already full rocket), fly for one hour in an extremely bare bones flight that literally feels like a roller-coaster (so forget any kind of phone access, you'll be lucky not to puke while just holding on). Then you'll arrive at your destination landing area, ready for some limo to take you on another three hour trip back to civilization.
So you've saved maybe 8-10 hours, being extremely generous and only for the longest haul flights possible, but got none of the luxuries you'd expect. And you get to pay much more for the whole deal.
Remember that the Concorde halved or less the Paris-New York trip, and gave all the luxury you could want, and still went out of business.
According to SpaceX themselves [0], the axial acceleration can reach up to 6g, though they do say it can be throttled, so what can be achieved in practice remains to be seen. Some graph on reddit with no other context is hard for me to trust.
The link I provided sources the data from an actual Starship flight. Just cause it's hosted on Reddit doesn't change the data. The link you provided was put together before flights even started from simulations.
Concorde stopped flying for lots of reasons, not the least of which is that BA was the only one flying them by the end. In a different world, had there been a robust cargo program (and a reason for one), it would not have been on British Airways to run the program by themselves and the program would have continued. This is hypothetical, of course, but the rockets are flying to deliver cargo (and people) to space anyway, so there's a lot of expertise being built up that doesn't depend on a passenger service.
I don't know if rocket passenger service will ever happen or become routine, but there's just so much to the Concorde story that simplifying it like that isn't a good case study that does the program justice.
He's already landing Starships in oceans.
People today pay $15,000+ USD per seat now for 1st class, and it still takes them 18+ hours.