A few students have brought to my attention a few videos on YouTube of foreigners promoting their language-learning methods or teaching Japanese (using English, of course), and they asked for my opinion.
I'll talk about a few YouTubers that hopefully readers can identify based on the description. I don't want to name them and give them any more attention, because I don't think that they really deserve any attention in regard anything pedagogical really. It's best to stay away from them and learn Japanese from Japanese natives, especially teachers with teaching credentials.
I should also state that I don't have the time to watch video after video of these people, but I did watch at least three or more to get an idea how they explain some topics like は／が but mostly to see how their spoken Japanese was.
This guy's entire channel was nothing but promoting his language learning method and tips, almost 100% in English. My students told me he apparently studied in Japan for a few months and hasn't come back. He now just makes videos on YouTube and asks for money on a website called Patreon.
I watched his videos where he spoke Japanese and I would put his ability around lower-intermediate. When I say that I mean in terms of Japanese standards, not necessarily the standards of learners. The videos where he had conversations were very simple. Having said that, he did have fairly decent pronunciation, but the Japanese was so simple that it is really hard to judge his ability based off that alone. He did make a few grammatical errors (nothing too serious), but beyond that, it seemed he memorized phrases based off of a recording that his speech sounded robotic, or monotonous. He would almost always talk at the same speed and same tone, rather than say anything quickly or slowly as the conversation progressed. Because of this, I would say his ability is lower-intermediate and that's the level I would put him at my school.
This person's entire video catalog is with the persona of a robotic girl using a kind of speech synthesizer software. Not only is the English pronunciation strange at times, but the Japanese intonation is rarely correct.
I watched a few videos to get the gist of the content. The lessons were mostly correct, but for people learning Japanese through English, I would say it's okay. The only thing I should note is that this person is clearly a native English speaker and not a native Japanese speaker.
I can't judge this person's actual speaking ability because of the speech synthesizer, but I have read some of their Japanese-written comments. There were quite a few strange writings that make it a dead giveaway that this person isn't Japanese.
While I briefly mentioned two of the most brought up YouTubers, I would like to mention how I feel about some of the others that I've seen a few videos from.
Basically, I haven't seen any that I would consider advanced by any means. Now, I am specifically talking about language gurus and their Japanese ability. There are many YouTubers that just do other types of videos about Japan that I would ascertain that they are advanced, but they don't try to teach the language.
I know if you're a complete beginner, it is hard to learn Japanese using only Japanese, since you don't know any words and you haven't mastered the sounds. It may be fine to learn from videos using English to explain some Japanese, but the best way to learn Japanese is through Japanese.