Actually the need to change frequencies is real. I've noticed that the sector changes (the reason for the frequency change) are pretty close to real world. I've never had enroute vectors, I usually file GPS-direct, or airways. The only vectoring I get is the last part of the flight on the way to the approach. Then I usually bypass that by picking an approach that has a transition fix, which allows me to fly direct to that fix and the approach with no vectoring.
I'm an instrument rated private pilot so I have some real world experience with this. Maybe it's just the flights I've done in FSX, but they are nothing like my real world experience. FSX ATC gives you a frequency change and as soon as you get there they give you another, often right back to the one you were on. What I've seen is not like the real world and it seems like it ought to be fixable.
Same with the constant heading changes. In the real world heading changes are infrequent. Usually ATC lets you navigate and only gives you heading changes when they need you to avoid something else. The constant back and forth is not real.