I'm sorry but this is one of the most incorrect things I have ever read. If I could downvote it twice I would.

It's true that Japanese tend to be more strict about accurate production of phonology than many other language speakers but speaking and writing are huge enablers of becoming better. It's really not that hard to unlearn bad pronunciation especially in an immersive context. Also most Japanese have a tendency to gently correct a speaker if you use the wrong phrase, particle, or construction.

Obviously if you've been self-learning your first few conversations with real people are going to be rough and so maybe avoid dense topics like Japanese attitudes on the JSDF. But if you end up in a light conversation circle where you talk about your favorite foods you'll be fine.

Fixing a bad habit is very hard, and I clearly stated it that outputting is very helpful, but you need to be constantly corrected or you'll develop bad habits that are very hard to fix. I'm not a native english speaker and I'm in a community of immigrants in the US and most of them have developed very bad habits that are fixable, but would require major effort and time on their part. The main ones being that they do word-level translation from their mother language to english and keep the same sentence structure, or borrowed words that are common in both languages are pronounced in a half-half sense, i.e. they change how the words are pronounced to make them sound more english, but the vowels still sound spanish/portuguese/etc.

Also note that these are not barriers to being understood, but they are barriers to be fluent in the language. These people have lived in the US for 10+ years and communicate in english just fine, humans need very little language to communicate most things. But if they need to be taken seriously in jobs that require constant communication, becoming fluent should be a long term goal, and outputting early is bad. It's best to wait for 1-2 months until you get a grasp of sound and flow of the language.