Looking at all the things that make German hard to learn (e.g. 4 grammatical cases for 3 genders, tons of irregular verbs, different pre- and suffixes for the same meaning...), I don't get the joke "haha look at that long word".
They're perfectly readable unless you skip on learning your vocabulary. So what you're saying is you haven't been doing your homework.
Nahrungsmittelunverträglichkeit:
- Nahrung - sustenance
- Mittel - resource or means
- Nahrungsmittel - means of sustenance, foodstuffs (the s ist just a connector without meaning)
- un - negating prefix, as in English
- verträglich - tolerable, agreeable, so "unverträglich" = intolerable
- keit - a suffix making a noun out of the preceding adjective, so "intolerable" > intolerance
Oh, I don't. And I don't mean to rain on your parade, you do you.
I just don't think it's a good joke because it stems from ignorance.
Edit: I guess I am taking it too seriously. Fulfilling the cliché of the humorless German, fantastic.