That's right. If I remember right, one of the top ways that the 1% earn their wealth is by taking bank loans with things like stocks as collateral. Since they never cash in the stocks, they technically have zero income.

If you don't directly tax assets, or otherwise broaden the definition of income to include assets (though that'll take some serious lawerying to make ironclad), no amount of taxing the wealthy will make a serious difference. Only those that have shitty accountants.

Even then, you'll always have to watch out for those wealthy just fleeing the country selling off any asset they can't take with them, screwing over the entire country.