Great post Mike, I absolutely love following along with your thought process here. For me, that 12/30/17 DwD is ALL about the dark D dorian jam around minutes 16-18.

One counter argument to your point is that I think Phish, and specifically Trey but to some extent Page and Mike as well, are doing far more with timbre than ever before, and that Phish's main musical experimentation and exploration at this point in their career in along the lines of timbre (tone color, or the "sound" of the instruments, to anyone unfamiliar with the musical term). Consider that Trey has basically had the same hardware and path signal through pedals from around the late 1980s until 2015, with only minor tweaks and additions here and there. In 2015, Trey overhauled his rig. After the Baker's Dozen, Trey again overhauled the rig and installed a new custom pedal/effect activation system, overhauling the mechanism with which he experiments with sound. In the span of 2 years, Trey has done more tinkering with his sound than he had for the previous 25.

This has led to an explosion of experimentation with timbre, much of it in the department of digital delay and echo effects, but also a lot of it having to do with exploring different combinations of pedals and effects modules to create new combinations of sound. You can hear this throughout the NYE run - there's one moment during "Soul Planet" where Trey accidentally stumbles into a combination of pedals that lead to practically no sound coming from his guitar when he's playing! What this means, to me at least, is that Phish has shifted their pitch-based musical exploration - melody and harmony - to a timbre-based exploration. Page and Mike are doing it too (especially Page with his new synths during Baker's Dozen). For me this came to a peak during that dark DwD jam, as all three melodic instruments were deeply ensconced in murky, growling, sinister timbres, and of course the meterless noise jam after "Steam" when Fishman also experimented with his new sound toy, the Marimba Lumina.

For fans like yourself who listen in large part for pitch-based experimentation and weirdness (I include myself here, too!), it's no surprise that jams are sounding more and more similar. I agree - from a pitch standpoint, there is a lot of repetition. I find myself constantly hearing the same kinds of subdominant jams, and wishing they would find some other kinds of progressions to explore (I still love everything I'm hearing these days). Yet maybe our issue is that we need to change our mode of listening and expectation, and shift ourselves to listen for timbre rather than only hearing it as subsidiary to pitch.