The Zumba instructor did not make an introduction to new people. As I stated in the OP, I didn't see the woman she called out. If the woman was doing her own thing (as opposed to simply not being able to keep up), I would think that was rather rude to do in a group setting. Either way, I think the instructor should have called her out if it was a safety issue and said something helpful like telling her to march in place and be careful of those around her instead of just scolding her and telling her she was messing people up. I was really surprised that woman stayed in class and didn't just get her things and march out.
As a licensed Zumba instructor I am mortified on behalf of my colleague!
I have learned over the years that Zumba classes are very instructor specific. I love Zumba but there are some instructors whose classes I would never take; not because they are bad but because they are...just stylistically different. Different energy. Different intensity. Different music. Though Zumba is not supposed to have different experience levels, you may walk into certain classes and get a very "Beginner" or "Advanced" vibe.
Though each instructor has their own style, IMHO some things in class should be a given. If there are new people and/or a new dance, the instructor should give an intro. They should always give adequate visual and verbal cues to help people learn the choreography. They should show alternative movement options to some of the more difficult steps.
Zumba is supposed to be a dance party. That's our dingitydang MOTTO for crying out loud - "Ditch the workout, join the party." No one "scolds" people at a party!
If a person is "doing their own thing," (which I have actually heard instructors encourage) I don't think it needs to be discouraged as long as their improvisation does not bring them into other people's space. I for one always took great joy in seeing one woman in a class who always "did her own thing" - it was quite creative and entertaining.
I have a hard time believing that someone, especially someone in the back, would distract others. Why? Well, as I tell anyone who is self conscious and worrying that everyone will be staring at them: "No one is going to be looking at you - they will all be looking at me so they can keep up, or if they look anywhere it will be at themselves to make sure they're doing it okay."
When I was first learning, I will admit to watching the students who stood closest to the teacher - they usually were veterans so if I lost sight of the teacher I could go off of them! Otherwise I was never "distracted" by any of my classmates. Just inspired and entertained.
If a student was really flailing, I might yell some general direction like "Watch your spacing, be careful of your neighbor" and hope that brought them back on track. Or as mentioned above I would remind people to just march or keep it low key when they felt lost.
Berating a student, publicly or privately, is unacceptable. You might try and tactfully suggest they explore a different class, but a good instructor realizes it's ultimately the student's
time and money and treats them accordingly. Which IMHO means either giving them instruction and helping them succeed or giving them space and leaving them to their own devices.
PS: I hope your experience didn't sour you on Zumba OP!
And I hope any instructors or aspiring instructors who read this realize how such rude behavior can be "professional darwinism."