Restricting access to the PCT is not going to work for one basic reason: you don't need a permit (or, if you do for short runs, there aren't (m)any quotas) to hike major parts of the first 700 miles aka the Desert section NOBO. Or, conversely, a lot of Oregon/NoCal north of Tahoe for those going SOBO.
Secondly, the permit system was established under the assumption of balance. That is, the entry & exit points within the parks and wilderness areas are expected to roughly balance out. Where the hitch then comes in is someone hiking from outside the "premier" zones into the parks, and then either exiting or continuing through. If no permit is required to enter (or they are issued, but no quotas exist), then how does a government entity deny exit?
The same hitch in regulations is now being used to hike the JMT. One can either start outside YNP @ Tioga, or start below the JMT @ Horseshoe meadows. Now, consider a long ass section hike (LASH) on the PCT: I jump on somewhere out in Tehachapi with my exit Lassen NP. I cannot foresee any condition where I would be disallowed to walk thru the Sierra Nevada.
In order to incorporate all entry/exit into the permit system, the entire range of travel would need to be included. This introduces the next level of push-back, because people who live in the those regions, or casual users, are not going to accept that they now need a permit (and definitely not a quota) to enjoy an area that always had open access. Try explaining that restrictions are in place due to a seasonal flow of hikers (temporarily) passing through either their direct area, or more accurately, 400 miles away in the Sierra Nevada.
If you look at traffic statistics, while the Sierra is being impacted, it's only relative to those who have memories of conditions before the PCT became popular. Overall, the true impact is minimal compared to what is occurring during the first 250 miles. This is where the largest volume is happening (before many hikers begin to drop out).
Once again, we need to remind ourselves that population growth is here and the impact is really beginning to be felt. The Valley long, long ago gave up the ghost as to any pretense of a peaceful, outdoor experience. The High Sierra will always present more of a challenge, but communications and equipment technology is making it both easier to access, as well as provide entertainment for those not necessarily into the full 'outdoor experience'.
You can become upset and waste your precious time fighting reality, or you can shrug your shoulders and get on with your life. Like I've mentioned a few times already upstream, everything we're seeing in backpacking already occurred a long time ago in surfing. That includes the frustration & push-back, as best exemplified by this short clip from 45 years ago:
https://www.youtube.com/watch?v=3uHs3E9tva8