Is telling someone to move on mean?

Probably should never tell anyone to move on lol you dont know that persons emotions, what they been through or how they see it. You have to let them move on on their own a d let them heal the way they need to heal just be wupportive if u feel they talk about it alot and ur annoyed its better to tell them they talk about it alot and thats not helping them heal versus telling someone move on lol

Yes, of course. Mind your business.

Depends on context, but it usually sounds like: "Just get over it"

A better way to say it would be something like: "You deserve better" or "You might not see it now, but things will get better with time"

No it’s not. But saying “I don’t think I deserve you” probably rings very hollow to them if they want to stay in the relationship and I would bet doesn’t sit well at all.

Why would it be mean, unless you insulted them or something.

In some circumstances, I reckon, it is.

My wife didn't say "move on" to her fwb's in college, but when they started to get too serious, she did tell them it was better for them to stop dating each other. She managed to do it in a way that preserved the friendship. She didn't want them to think it was possible that she would dump me and choose them.

I need to tell someone this.

Depends on how one says it. It can be compassionate or snarky/sarcastic depending on context and tone.
It can show the listener doesn't understand and couldn't care less.

It can also be very supportive, if the person seems to be "moving" already, it can be just what they need to hear.

I don't think it would be

Imo it's stating the obvious. If a healthy mental situation is going to be had for the person, they must move on. That can look different for different people but it is necessary. . .and can be easier said than done.

Context

It's awkward when you don't feel you don't deserve someone, and you are looking to let them down politely? Most when they are feeling hurt also want to feel you are hurt.

No not mean, but it's not anyone's place to tell others when or how they should be over something. Saying it's not going to make it happen anyway.

Telling someone to move on could have several different meanings, depending on the circumstances and whom you are talking to.

I was in your shoes and told someone to move on. So one day he did and now we both regret it.

A lot depends on the situation .. and how its delivered / phrased

I wish my crush told me to move on.
I would respect it

It is what it is. It’s better than leading them on.

Yup