Defining "the rich" would help. Arguably someone making their money on income is not "rich", they're still moving up the economic ladder. Someone making capital gains, especially exclusively or in majority, is definitely rich.
There's also wealth taxes. Currently a lot of places implement income taxes which actually slows down or halts economic fluidity.
The solution to "it's too hard to penalize the rich" isn't to give up, it's to figure out how they hide their real income and take that into account.