This is very common in Chinese now. The older generation, many of whom didn’t learn pinyin, just use voice input to send messages; the younger generations just use pinyin input and similarly can’t handwrite beyond the simplest characters.
The phenomenon of forgetting how to write is called 提笔忘字 (tíbǐwàngzì - to pick up the pen and forget the character). It was previously covered here on HN: https://news.ycombinator.com/item?id=41959256
Not really. Even in English there are only a few possible ways to spell out a given sound. With Chinese characters that mostly goes out the window, making speaking and writing more or less orthogonal skills. Not entirely since there are classes of characters that are related by sound, but to a much greater extent than alphabetic languages. Personally if I forget a spelling in English or a related language I realize that my approximation looks wrong and can correct it by elimination, whereas with Chinese characters it's common for people to simply not have a clue how to even write the first stroke of a word they've heard and read before.
The phenomenon of forgetting how to write is called 提笔忘字 (tíbǐwàngzì - to pick up the pen and forget the character). It was previously covered here on HN: https://news.ycombinator.com/item?id=41959256