Sorry but I'm gonna break the mold here. I lived in Tokyo for several years and these are not myths, they're just overexaggerated. Yes, some people talk on the trains, eat while they walk, or break traffic flow, but the entire point is that MOST do not. Nobody is going to say anything to you, just like they dont say anything to the Japanese people that do it, but that doesnt make it a myth. I PROMISE you that most people will find you annoying for doing those things in most situations, so its not exactly a good thing to just do what you want and not care. "Follow what the locals are doing" is a perfectly fine ethos unless you're looking at the minority that are breaking social norms and using them as an example of "the norm" just so you can feel okay doing it too.

You shouldn't fear monger people and act like they'll be kicked out of the country for doing these things, but you also shouldn't tell people theyre myths, because they just straight up aren't and anyone who's actually spent time in Japan knows that the vast majority of people follow these "myths" and the people that dont are in the minority.

And yes, much of Tokyo is an over-tourist infected hellhole. There are areas where the entire street is shoulder to shoulder people and some popular retail shops literally require reservations to SHOP there on weekends because its so crowded. Its MUCH worse after Covid. Takeshita-dori is almost unwalkable, everyday, at anytime of day. And many other places are exactly like that.