Somewhat related...
In my view, far and away the biggest impediment to overtaking is circuit design. There's simply no degree of possible modification to the cars that can counteract the inherent futility of running them on circuits that predominantly feature only a single racing line, because it will forever be impossible for two cars to occupy the same space at the same time. Even Hermann Tilke's fetish for so-called "point-and-squirt" layouts has done little to improve matters, because the tendency for competitive strategies to converge upon the optimum is absolute, meaning it includes driving lines.
The problem isn't all that difficult to solve; there just doesn't seem to be any will to acknowledge it, much less address it. If you widen and add positive camber to only a handful of corners, preferably those that lead onto the longer straights, such that the difference between the the optimum and sub-optimum lines is reduced, you will have permanently solved the "structural" problem of overtaking, and DRS and silly-putty tires can be relegated to the ash heap of history. The only obstacle that will remain is the natural tendency for faster cars to start ahead of slower cars, but that problem can't be solved without complete standardization or a wholesale change to how races are organized, both of which sorta cut against the grain of F1's founding ethos.
If such a change to circuits ever occurs, I suggest we all pitch in and build a monument to the glory of whomever made it happen.