I know one of the arguments that I heard and found persuasive is that wealth taxes incentivize the rich to get better at hiding income. Which isn't to say that I don't think it's a fight worth having. I just don't think it's the silver bullet solution that some people (Bernie, Warren, AOC) seem to think that it is.
The country of Greece is probably a good case study here.
Anyway, to piggy back off of the comment @Gromnir made, thank goodness I don't hear libertarians trying to pull that "flat tax" bull**** anymore