Finance is sort of a unique beast in that the field is inherently negative-sum. The profits you take home are always going to be profits somebody else isn't getting.
If you're doing like, real work, solving problems in your domain actually adds value, and so the profits you get are from the value you provide.
If you're algo trading then yes, which is what the person you're replying to is talking about.
But "finance" is very broad and covers very real and valuable work like making loans and insurance - be careful not to be too broad in your condemnation.
If you're doing like, real work, solving problems in your domain actually adds value, and so the profits you get are from the value you provide.