A few factors to take into account.
1. Japan's intrinsic distaste for change. New ideas = innovation; if old men are the only one's with the last say, don't expect much.
2. Crackdown on Japanese online media. Lots of blogs and sites were forced to close with claims that they were infringing on copyrights. Also goodbye to mediafire, megaupload and other easier ways to share music. AND most integral (for me at least) jpopsuki torrent tracker/forum went down for a LONG time.
3. Those like myself who were around for the JPop Boom of the mid-late 2000s are kind of old now.
I got into JPop around 2005 at age 14. I'm now 21 gonna be 22 next month. I got back in JPop only due to luck of the draw, that I will be going to Japan this year (in 5 days to be specific) so it's kind of a language tool.
I also like KPop too. I don't see why people have to shit on it so hard. It's the mainstream stuff that's interesting (non-mainstream KPop is really bland) kind of like the inverse of the Japanese industry. A few more words of wisdom to kids and teens out there:
Do not place yourself outside of what is mainstream during your time. What is mainstream in your country today won't be forever, enjoy it while you have it don't put yourselves in a bubble especially of music you can't fully understand. It's something I only realized when I entered college. You want to be well rounded, strive for that, get all up in your JPops and learn Japanese too, even. Just don't isolate yourself or you'll be come a stranger to your own country and an inevitable stranger in Japan (since if you're not Japanese, you'll never be accepted there)