[otikik]

That's the first thing that I discovered when I visited Paris for the first time.

No one says "Nous", there, ever. Perhaps the politicians, while giving a speech. Everyone else uses the more informal "On".

I felt duped by my French classes.

[mijamo]

Older generations sometimes do. My grandma and her sisters nearly never uses "on".

It is often used for larger groups or when the group is not very personally connected. For instance when talking about your company doing something you will often use "nous". I would also use "nous" to refer to the whole list of invitees to a wedding. And in formal contextes like research papers, reports etc. You would never use "on", always "nous".