yeah im not sure how prevalent it is now but in my city in ages past it was pretty common to talk at public transit stops and grocery lines and such. I mean there is a casual way to strike up a conversation and a creepy way and movies by and large have these two. Even comedies about someone seeming creepy who did not mean to.

Before social media this was totally normal.

That depends so much on where and when you are. I'm older than social media and no, strangers didn't walk up and say hi in my culture/s. There were plenty of places that sort of thing was acceptable but they were places with an implied invitation to socialise, not the street.

I grew up without social media and to me this is not at all normal. The only strangers who talk to you want to sell you something, or they have some mental issues.

Sadly, some of us are unable to 'take a hint' as it doesn't seem like a hint. Not everybody is wired to pick up on small contextual cues and may only notice the big ones; being in a public shopping mall (historically a pretty social location) while not shopping, implies to my brain a desire to be around people, even if you aren't there for the buildings intended purpose. It's definitely fine that your intention wasn't to be social, I don't desire to be social and try to avoid places with people like the plague.

I don't think he did anything wrong either though; the few mall walkers I've known almost consider it a sport so I get why he would say those exact words (not seeing you during their usual meetup time, he was likely inviting you to walk with their group).