Yes, it is difficult even for Chinese native speakers. Character amnesia is a thing.

Read for example this classic essay

http://www.pinyin.info/readings/texts/moser.html

written by an actual linguist.

So it is. Rather like how the English word order rules are particularly difficult, e.g. look at the weird table in http://grammar.ccc.commnet.edu/grammar/adjectives.htm, or German plurals.

Most children learn their native language(s) properly at about the same age, which suggests that the languages are comparably difficult to learn, and perhaps that if a language takes too long, it'll be simplified. But there's nothing that pushes languages to have the same difficulties.

An important difference is that English lets you get your point across even if you mess up word order, conjugation, and/or spelling. With logographic systems, there is practically no connection between written symbols and their sounds. Even competent writers can know what a symbol means, but not know how to pronounce it. Or they'll be able to use a word in speech, but not be able to write it down. The first time I saw this happen with native Mandarin speakers, I thought they were playing a joke on me.

The main advantage of logographic languages is written information density. If you've ever seen a Chinese or Japanese copy of a Harry Potter book, you'll understand. (They're quite thin.) Also, Twitter is a totally different experience when using hanzi or kanji. The character limit is enough for a paragraph instead of a sentence.

We are talking about written languages, not spoken.

Moreover I find your last sentence to contradict the previous. I don't know what you are trying to say, but you are talking about a different domain.

I'm curious. Why?

I know there have been attempts to each people purely spoken language and purely written, but those are rare. In practice the two seem strongly connected.

Using adjectives in the “wrong” order doesn’t really change the meaning significantly though, it just sounds a little weird to a native speaker.

I don’t think anyone claims that spoken Chinese is particularly hard compared to other languages, but that the written form is measurably harder than languages that use an alphabetic orthography.

(I have read claims that Russian is particularly difficult though - can anyone comment?)

>(I have read claims that Russian is particularly difficult though - can anyone comment?)

In what way? It uses an alphabet just like Latin-based languages, and it's more phonetic than English (but not completely phonetic). I'm sure anyone can learn to write/read Cyrillic in a few days if they already know Latin. The actual language is harder than English because of large number of noun/adjective declensions (depending on plurality, case, gender) which would be a pain to memorize for a non-native. But being an Indo-European language it's still pretty similar to English as far as languages go. Chinese, having a completely different writing system, completely different sentence structure, completely different fixed expressions, completely different sounds (and tones!) is orders of magnitude harder.

Chinese sentence structure is in many cases identical or very similar to English, and follows the same general word order, Subject-Verb-Object.

Yeah, the better example for English would've been the spelling. Ghoti and so on, dyslexia is a significant problem. https://en.wikipedia.org/wiki/Dyslexia#Language

My wife knows Russian and 5-6 other languages on a tourist level or better. She says Russian has both a difficult and a simple aspect: Newspapers use a large vocabulary so reading with moderate education is tricky, but people's accents are easier to deal with.