> taxes are very high
Doesn't seem so: Croatia's tax to GDP ratio is 26.6 %. Compare that to 46.8 % in Belgium, 43.4 % in Austria, 40.6 % in Germany, 45.8 % in Sweden. 26.9 % in U.S. which is internationally known as a low-tax regime.
Surely some taxes are high, and taxation is not necessarily fair, but I'd say that Croatia's taxes overall are not high. I would also expect that the "black market" GDP is higher there than in "old" EU countries, say Germany or even France, or the U.S. Though I admit this is mostly based on just prejudice.
(Using Heritage Foundation figures in http://en.wikipedia.org/wiki/List_of_countries_by_tax_revenu... - OECD numbers are slightly different but not that much)