This may contribute, but it's not the main issue imo. I've worked with tons of Japanese devs and English didn't hold them back much.
Plus look at Ruby, which was all the rage in webdev at one point. It was invented in Japan, and it had better documentation in Japanese than English.
Bigger issues for Japan's tech industry in 2023:
- Lack of VC/Startup investment (0.02% of GDP vs. 0.52% for USA)[1]
- Lack of government support
- Lack of strong CS university programs
- Risk-averse culture (failure is congratulated in the US but condemned in Japan; people don't want to risk building a startup)
- Continued prevalence of "System Integration" rather than in-house dev teams
- Outsourcing of dev work to cheaper countries (India etc).
- Difficulty of moving to Japan (visa issues, high taxes etc; hard for immigrants to start businesses here)
[1] https://www.boj.or.jp/en/research/brp/ron_2021/data/ron21031...