It's lazy, but from what I have heard from people I trust (which itself is lazy, since I haven't searched journal articles) is that there is absolutely no scientific evidence that Ivermectin is a useful therapeutic for covid infection.

You are correct that the "horse dewormer" meme was due to desperate people buying industrial amounts, not human amounts, from vet supply shops. It's worth mocking because these people are desperately avoiding mainstream medical advice per se.