Are Ancient Greek and Modern Greek as Far Apart or Similar as Old English and Present English?

There is a strongly held belief that Aristotle pronounced Greek identically to modern Greek. Modern Greeks just pronounce ancient Greek as the modern language. A huge number of diphthongs and vowel sounds still retain their old spellings. The consonant system is sort of interesting in that it has voiceless, unaspirated, voiceless,. And then it has a few voiced for stops and one or two syllabones.