It kinda feels like kicking someone while they're down to criticize PS5's performance in Japan at this point, but yeah, it's not exactly a good sign that week after week passes with no PS5 software in the top 30 and hardware tracking behind the Wii U of all things.
Once supply can be sorted out and some actual next gen games arrive things should pick up, but lifetime I expect it to continue the decline PS systems have shown in Japan since PS2.