Comment by matusp

Cyrillic is probably a successor to Glagolitic. Glagolitic was the first Slavic alphabet, but when they tried to use it in Bulgaria, it had all the UX problems you mentioned. What they did is replace most of the characters with their Greek counterparts, while keeping the Glagolitic writing system and some of the characters with no counterparts. Bulgaria was close to Byzantium, and people were more likely to know and use Greek letters already. Nevertheless, Cyril and Methodius should still get some recognition, as the shape of the letters is not as important as having the system to write down the Slavic language into letters.