Icelandic may be the most grammatically complicated language on earth. It is nearly unchanged from Viking times. Most European languages, including English, have become more analytic and less grammatical over time, losing a lot of inflections, conjugations, etc. But Icelandic has it all. Multiple cases with the noun and modifying adjectives (and articles) changing form each time. Multiple verbal conjugations depending on person and number. Masculine, feminine, and neuter nouns.
They take pride in their ancient language and avoid anything that might “corrupt” it.