I think there is no question that you can get bad habits. A mountain of input won't fix everything. I know this because I have seen it
One of my students in Japan was 60 years old. Her brother left Japan for the US when he was 20 and lived there for 40 years. During this time he almost completely forgot Japanese so my student was studying English to be able to communicate with him. I read his emails. He had a native level vocab and used idioms, however he made quite a few mistakes and overall it didn't feel natural.
I have also studied Japanese in a class with Chinese girl who was married to a Japanese man and lived with his whole family. She was getting a huge amount of Japanese input and speaking lots everyday, yet over the 6 months I studied with her her speaking skill remained child like and contained many mistakes. I think she met him in China and whilst her Japanese was poor spoke a lot and made a lot of bad habits. I think the problem is you don't need to understand every nuance of a language to understand what is said to you. Some people with bad habits just ignore the finer details eg 大阪へ行きます、大阪に行きます, and just use the one they have always used.
I think the big danger is when you learn grammar rules first and then use them to speak. This is very different from allowing the words to come from your past input experience and can create long lasting bad habits.
However, I think output is a skill and I agree it does internalise the language. The more you output the better you will get at it. It is just that there are dangers. I think the advice that if you can't say something complex, then make simple sentences or use examples to make your point is a good and safe way, much like a child does.
Pretty much every Japanese person and infact every person I have ever met has believed that you need to speak a language a lot to get good at it. Europe may be different, but I think this is the general belief in primarily monolingual countries. I have tried many times to get my students and friends, who have studied English for years but still suck using AJATT based methods and they never do it. It's frustrating.
One of my students in Japan was 60 years old. Her brother left Japan for the US when he was 20 and lived there for 40 years. During this time he almost completely forgot Japanese so my student was studying English to be able to communicate with him. I read his emails. He had a native level vocab and used idioms, however he made quite a few mistakes and overall it didn't feel natural.
I have also studied Japanese in a class with Chinese girl who was married to a Japanese man and lived with his whole family. She was getting a huge amount of Japanese input and speaking lots everyday, yet over the 6 months I studied with her her speaking skill remained child like and contained many mistakes. I think she met him in China and whilst her Japanese was poor spoke a lot and made a lot of bad habits. I think the problem is you don't need to understand every nuance of a language to understand what is said to you. Some people with bad habits just ignore the finer details eg 大阪へ行きます、大阪に行きます, and just use the one they have always used.
I think the big danger is when you learn grammar rules first and then use them to speak. This is very different from allowing the words to come from your past input experience and can create long lasting bad habits.
However, I think output is a skill and I agree it does internalise the language. The more you output the better you will get at it. It is just that there are dangers. I think the advice that if you can't say something complex, then make simple sentences or use examples to make your point is a good and safe way, much like a child does.
Pretty much every Japanese person and infact every person I have ever met has believed that you need to speak a language a lot to get good at it. Europe may be different, but I think this is the general belief in primarily monolingual countries. I have tried many times to get my students and friends, who have studied English for years but still suck using AJATT based methods and they never do it. It's frustrating.

