Those blocks also quite often map to morphemes, so the grouping isn't just syllabic but also retains higher-level morphological information. The orthography prefers letter distributions over groups that keep the same morpheme spelled the same way across use in different words. This promotes morpheme re-use, which is great for context learning.

Letter shapes are featural rather than arbitrary, e.g. a consonant might visualize the tongue position used to make its sound. And yep letters graphically build on each other (normal to iotized vowels and normal to aspirated consonants are all formed the same way, respectively, by adding a stroke).

Hangul is a masterstroke of human cultural achievement. Had a lot to do with me emigrating to Korea! I agree with you that there's a lot of geeky audience appeal to it (including even its origin story of a bunch of smart people applying state of the art knowledge of the day to enable others by freely disseminating it).