That's very pedantic! While I didn't mean "it" in that statement to refer just to the word "lazy", I suppose it's true that "being lazy" also isn't technically a verb. Other commenters below have found more precise language, but I think a charitable reading of what I wrote is pretty clear in meaning.

How about "stop [acting] lazy"? 'Acting' has more of an implication of something you are putting on that can be easily changed, rather than 'being' which possibly implies something you are, that is not easily changed.

This is deeper down a rabbit hole than I really meant to go, but I personally think "being lazy" is appropriate; I spend time being lazy pretty often, and it isn't an act, it's true laziness, but it's also temporary.

No, but "being lazy" is an action, which can be stopped. It's much harder to stop being lazy if you are being told it's a facet of your identity.

Lazy, here, is a state. It could be understood as a temporary state like being asleep or being hungry, or a facet of one's identity.

"Stop slacking" might be better; it unambiguously refers to current behavior that a person can change immediately.

I thought that maybe another language would have a word for this, and I found

https://spanishto-english.com/spanish-dictionary/haraganear

It calls "being lazy" an intransitive verb

Lazy is an attribute.

"Being lazy" is a transient state.

That's the important distinction here.