They are a replacement for non verbal communication such as a head nod, or hand wave, or a smile. Not a way to express a full thought in and of itself.
I suppose the context of the conversation matters. I always check who left what emojis to get a feeling of the room, but I'm usually in smaller rooms where I know the people. In a larger discord for example with many strangers, I think your right in an individual level, but as the poster of a comment, it still helps gauge the general temperature of the audience, so too speak, regardless of who is on the hook for continued conversation. Not sure I would notice a head nod if I was speaking in a room to hundreds of people anyways though.
I'm not saying it's superior, but I appreciate the nuance's it can bring to online dialog where otherwise many misinterpretations are likely to happen
People mark an emoji and then keep scrolling feeling good about themselves.