If my students were only posting cat videos, I wouldn't have a problem with this, but most of the posts were meant to start discussion or get feedback. For these kinds of posts, "like" doesn't mean anything.
Before Facebook and Twitter, if you wanted to engage with somebody's post, the only way (on nearly all platforms) was to make a comment. Writing and posting a comment takes at least a little thought and effort.
I'm not saying that "liking" is bad and everyone should stop it. What I am saying is this: think about what your "like" means.
Here's an example of a post where "liking" would be completely appropriate:
In this case, "like" simply means "yes."
On the other hand, think about what "like" means for a post like this:
In this case, "like" doesn't mean much of anything, except maybe "I approve of this idea, but don't want to contribute anything to it."
After that talk with my students, I noticed that they commented more and "liked" less.