A linguist once told me (angrily) that Japanese sentences do have subjects, they're just very easily implied from context.
It is worth pointing out that English also lets you omit the subject in some circumstances, namly commands. For example, we consider "clear your room" to be a complete sentence, despite the fact that it omits the subject, "you".
"[You] Gonna eat that pizza?"
"[I'm] Gonna go to the store."
"Where's John?" / "[He's] Eating."
Every country or people have their own ideas about how they are awesome, but I think I noticed it here because I'm an outsider.
To be honest, I'm quite sick of any cultural glorification from any country. But given how Japan never went through a cleansing after their fascism (unlike east/west-germany after '45 and '68) I can understand that there is not a lot of self-awareness in that regard.
In some sense the youth is trying to distance itself from the problematic past by becoming apathetic consumerists.
Every time one of these articles crop up, I feel that someone is viewing Japanese through some heavily rose tinted glasses.
But you'll find most spoken English sentences have I or You or a grammatically empty placeholder ("that is..." without antecedent or "there is...") as subjects. That's why other languages can omit them. It's pretty easy to guess which of those you mean so English could omit them eventually, too, with no loss of specificity.
You're on track with the "gramatically empty placeholder". We have expletive pronouns, like "it" in "it is raining", which one could consider to only serve grammatical purpose—it is only in the sentence precisely because the sentence must have a grammatical subject, not because the sentence has a subject in any semantic sense. There is some disagreement about this, however.
This is absolutely nothing special, there are hundreds of those: https://en.wikipedia.org/wiki/Null-subject_language