Having had two Pacificas now that both cool the same way, I'm confident this is an issue with the design of the Pacifica vs an issue with ones personal unit.
As an example, I test drove my 2020 Brand new. It was parked outside, and hot inside. I drove home to show it to my wife and kids, 12 miles through stoplights, etc, it took me about 25 minutes. The van was still not comfortably cool nor had the fan speed slowed down by the time I got home. If I were in my Lexus, it would have been fully cooled off and in low fan mode in maybe 7-10 minutes, and it has a black interior.
Its also not the first targe interior capacity vehicle I have ever had. My Lexus IS a 206 inch long long wheelbase sedan (6 inches longer than the Pacifica). I also had a 2015 Kia Sedona minivan, two Jeep Grand Cherokees, a Ford Explorer...all of which cooled better than either of my Pacificas.
The HVAC just doesnt seem to have enough cooling power or evacuation power to get all of the hot air inside pumped through the system and cooled.