Also after writing this, I noticed the inconsistency (from my view) that in English there are exceptions with words written uppercased, too, like "German", despite being an adjective and not a noun. Which might be irritating, as these words can also be used as noun (also for other words which are not nationalities and written lowercase), and there is no distinction between an adjective and a noun.

In German all adjectives are lowercase, all nouns uppercase.