Lego from my youth, which was a hand-me down at the time, doesn't fit well with new lego. So it might be 40 years old, (which seems like a long time until you actually reach that age!)
I think it's more likely do to plastic aging than the original tolerances though.
According to my local news outlet, they’re up 12% in revenue growth in the last year (which outpaces the rest of the toy industry) and up 1,200% since 2004.