Totally get what you mean, and @robert_gonzalez90 makes a good point about the junk being the same. The surprise of digging through a dusty bin and actually holding something weird is just gone when a machine guesses for you. Found a box of 80s concert tickets in a record store basement once, just sitting there waiting. That random luck feels way more special than a "because you liked" list, you know? What's the coolest physical thing you've stumbled on by accident?
Flea markets still exist though, you can go find stuff like that any weekend. The algorithm just shows you junk online instead of in person. Not sure it's really that different of an experience.