I don't think flying jets is more difficult than Warbirds, just different. It is an acquired skill, just like flying heavier planes was an acquired skill from the trainer aircraft we learned on. Anyone who can competently handle a heavy warbird could handle a jet, once they get some stick time and learn to anticipate throttle lag and the higher speeds. Hell, I think helicopters were harder to learn than warbirds or jets. That's both from a setup and a flying perspective.

Actually, I think a lot of pilots have trouble with nerves more than skills. It can take a while for some people to get accustomed to the fact that one bad decision could cost 8 or 9 thousand. I have seen some very competent pilots get trembly thumbs the first few times they have a big jet in the air.