kryptonians aren't same species as us,either.Jor-el is one scientist.That doesn't mean scientific consensus to say the least.For all they know jor el is a quack.All he had was earth quakes.krypton was inherently very hostile and unpredictable,for any real assessment.Think about it,These were superpeople that could have left the planet any time with or without any spaceship (Kryptonians had powers on krypton in some takes).But,they didn't.That means,they didn't want to leave regardless of whatever consequences that might happen.Also,a million years ago there where "humans".as you said,they weren't us.Even,if we go by thousands of year duration.We would still be a lot superior to people 50,000 years or 150,00 years ago.Also,exponential progress isn't exactly guaranteed thing.I believe,our rate of progress would decrease as well.If we look at history,progress/innovation leads to stagnation to different cultures.It took approximatley 100,000 years for us to start agriculture on a mass scale.