I used to take the train from Orlando down to Miami (well... Ft Lauderdale) and it was about 3 hours, vs a simple 1 hour flight, or a 3 hour drive. The train ride was worse on holidays though, sometimes it took 6 hours or even way longer. I think I'd much rather be on the plane overall.

Does your opinion change if the flight speed is 2500km/hour for most of the flight?

Sometimes it’s not that easy or cheap to build a railway. You have mountains, seas, wetlands etc. But I agree that high-speed trains should be the default option.