German-as-a-Second-language speaker here -
There's a lot of ambiguity and corner cases about what's a noun in German when you drill down to it (It maybe doesn't seem a problem coming English because you don't have to decide every time you write a word whether it's a noun or not). And Germans in highschool are drilled in this apparently, so many grow to hate it a bit. For example, take 'ein Paar'\'ein paar' (a pair) - in english you say oh pair is a noun so great. But in german whether you write it big or small depends on whether you're using it as an indefinite pronoun or a noun. You can apparently use it to distinguish a pair of trousers (in Paar Hosen) from a pair of trousers (ein paar Hosen), though don't ask me which is which...
And there are some fossilised expressions where even though things are nouns they're written small (e.g. 'durch dick und dünn' (through thick and thin.) ), and there are cases of capitalising things that sure look like adjectives though...I don't know how linguistics classify the parts of speech formally...
Or another example - if say "I take part" ("ich nehme teil") in something, is 'part' a noun? The german sentence is a word-for-word translation of the english, and 'Teil' is a noun in german (meaning 'part'), but you don't capitalise it because teil is part of the verb 'teilnehmen' and not independently a noun in this context.
(here's my personal menagerie of capitalisation rules for German: https://gist.github.com/increpare/b5d652b535656b794c47a77c1d... , and here's a relevant page (in German) by Duden, one of the two main authorities on German orthography - https://www.duden.de/sprachwissen/rechtschreibregeln/Groß-%2... . It's not a short page, and not something that comes intuitively to people. They learn this stuff).
All that said, I like German orthography! I enjoy compound words and (plus or minus edge cases) its approach to capitalisation.