Miki is right, Momusu used to be about individuality and rivalry (especially after gen 4 joined) and that was what made it fun. Also the anticipation of what style the new single would be and who would be grouped in album songs. Just when platinum era became really comfortable, everything got shook up with gen 9 and 10. They oozed personality and individuality again and together with the massive switch up from the 50th single onwards they got a renewed spark.
Until it all became extremely formulaic. I still have the feeling that I don't even really know 12th gen. I mean, there's so much focus on the group as a whole that all current members seem to just blend in. I bet that there are some really fun characters in the group, it's just that they are pretty much invisible at this point. They've got a new generation and there's hardly anything about them, they didn't capitalise on them at all.
I think 9th and 10th gen actually just joined at a good time when idols were coming back into vogue thanks to the success of groups like AKB and Momoiro Clover. I went back and listened to the singles from those couple of years recently and you know what? I felt like it was all super formulaic and predictable especially since they leaned so hard on a very small group of members and style of music. I don’t think it’s that 9th and 10th gens were idol powerhouses, they were just there at the right time. There’s not a lot of work to go around for idols and that’s why people feel like they don’t know the new gens. Can’t magically make opportunities arise out of nowhere. And the stuff that Up Front could do on their own probably either isn’t profitable nor does it increase the individual girls’ profitability enough to justify.
Morning Musume hasn’t been about rivalry in over a decade. It can’t be anymore. New gens audition together, they’re often promoted early on as a unit, and so much of popularity and promotion comes down to luck and happenstance and seniority that you can be ‘rivals’ all you want and it won’t matter. If a new girl came in and was the best singer MM had seen in 15 years would she be able to take Sakura’s place as a lead vocalist? No, of course not.