If users are posting replies which have no value, I’d suggest sending a PM and deleting the replies. And make a general post, perhaps a pinned one, setting out that you’re doing that, because the culture of the community is to have good conversations with substantive comments. But of course using the appropriate vocabulary for your case.
You might lose some goodwill and some users. People like to make low-effort comments. You are, for those people, trying to shift the culture, and you are changing their world.
If people are using short comments where they might instead use likes or reactions, then make sure they know that likes (or reactions) are appreciated and are the preferre alternative. Again, using the right language for your case.