Hanja characters which are shared both in the Korean language and also Japanese language are actually quite meaningful. So much so, that persons literate in Japanese and Korean can get the gist of phrases and sentences written in both Mandarin and Cantonese.
Hanja characters are basically pictograms, not phonemic representations, and are quite different from the glyphs that make up the Latin alphabet.
> Hanja characters are basically pictograms, not phonemic representations
This is language-dependent. In Japanese, for example, kanji can be used either for their semantic value ("kun" reading) or for their phonemic value ("on" reading).
For example, the Japanese word "futon" is written as 布団. The first character, "布", has a semantic meaning of "fabric", "spread out", or "disseminate", all of which are unrelated to the native Japanese word "futon". (That is, the word "futon" does not have a Japanese root meaning "fabric".) However, 布 is pronounced in various Chinese dialects as "bù", "buó", or "pu" -- which the Japanese language assimilated as the on reading "fu".
In response to a question I had in response to your post,
> Is Japanese language always/often a mix of kanji and hanja? Are there significant kinds of text that are kanji-only?
my partner, a native Japanese speaker, explained
> Usually mix of kanji, hiragana, and katakana.
> But some words are written only in kanji like “入室禁止” meaning do not enter (this room)
> For the sentences, almost all sentences require hiragana for verbs.
My buddy, a native English speaker fluent in Japanese, responded
> It’s usually a mix.
From which I gather: kanji-only signage and phrasing (which can be "read" by Mandarin or Cantonese literates) is common, but longer constructions involving sentences typically will have hiragana and/or katakana which are phonetic and have little to no meaning for people not literate in Japanese.