Why can't I change chords fast enough?
Try setting the tempo with your right hand, keep it steady and at speed, force your left hand to try and make the changes as best you can. It will get better as you practice making changes instead of playing slowly. And don't forget that there is no law that says every chord strum has to sound good.
Why is fingerstyle guitar so hard?
The quick answer is that, as you probably guessed, playing that material is difficult! They're playing incredibly complex arrangements that combine a variety of guitar styles, as well as right-hand and left-hand techniques. And they've been refining their chops for long time, so they play fast and with fluidity.