It’s not managing the glass that some people have difficulty with. I’d really say that falls under flying the airplane.Managing glass cockpits isn't too hard, at least if you grew up with computers and are in your 20s or 30s.
It’s managing the airplane. The flight crew, pax, ATC, company, etc. If you attempt a one man show with this, or just aren’t good at delegating and listening, you’re going to have a bad time.