...and then there's the Zoomers! Seriously is anyone under 40 a Republican?
There are under-40 Republicans, but you won't find any Republicans under about 28 or so. I know exactly one in real life, and I've literally never lived anywhere other than very white middle-class suburbs in solidly Republican states.
Also, I think the high Democratic turnout of the last few years won't go away when Trump is gone. For a long time we will be very determined to not let another Trump happen.
You obviously live in a massive bubble then. Pew consistently finds that among ages 18-25 only ~60% identify with the Dems while 30% or so lean R. That's certainly not "zero". Saying you know only one IRL is absurd.
