> So you get horrendous spellings if using Latin characters for the Slavic sounds, like you see in Polish.

I'm not sure where you get this from.

Several Slavic languages (Czech, Slovenian, Croatian, etc) use Latin-derived alphabets and managed to preserve their pronunciation with 100% fidelity. The Polish orthography is not the only solution to this, and I think it's a stretch to regard Croatian spellings as "horrendous". I am, of course, biased. But the number of characters in a word in Croatian maps 1:1 with its Cyrillic spelling, for example.