Truly, how do they even do these polls in the clusterfuck state of information transversal? Landlines, text messages, online shit?

Depends on the polls really. Mostly calling people and having nerds figure out the best way to call people. How many in this or that zip code and trying to keep track of the response rate. Online polls do happen but aren't as reliable because on the internet nobody knows you're a dog.

I would be very curious to compare the accuracy of polls pre-21st century to what we’re dealing with today

I would too. I remember on the 538 website they had the favorablility tracker for Trump/Biden and you could see other presidential terms. It seemed like there were barely any polls for like Truman so it was really blocky for the first few post war presidents. It probably just took time for people to get phones and for pollsters to get setup. Regardless, they were probably about as reliable if they had good methodology.