Looking back from time to time is fine. Do it all the time and you fall on your ass.
I'd say that even if the current Morning Musume didn't sing any songs from before 2011, they wouldn't be "unrelated" to the Morning Musume of 1997.
The continuity isn't in the selection of songs they sing, it's
a part of their very identity.
Just as a painter's identity isn't defined by their choice of brushes, Morning Musume's identity isn't defined by the songs they sing.
The songs are merely the tools that they use to paint the picture of their performance.
It only makes sense to use the ones that will give the best result.
What is the purpose of an "anniversary" in this context?
Is it to look back at the past and relive it, or is it to celebrate the fact that you've made it this far and are still going strong?
I think it's the latter and I believe the best way to celebrate is to put on the best goddamn show the members are capable of.
Unlike Dream Morning Musume, the
real Morning Musume doesn't exist only to perform old songs and make people fondly remember the past.
Morning Musume is a living, growing, evolving thing, and while it possesses a long history, it also deserves to have a present and a future.
While Morning Musume owes its current state to what has happened in the past, what defines it and gives it meaning is what happens next.
--I see. You're turning over a new leaf, huh?
Michishige: Of course, we have to value the things that our seniors taught us, but we shouldn't rely on those alone. I think a part of us depended too much on those. To be sure, the name "Morning Musume" is so great that there's satisfaction in just being accepted into the group, but it's not like that, you know! Although we can say that we've sold 100,000 units, in general, I don't think there's anyone, other than the fans, who knows all of the members' names. On the contrary, I want to treat this as the starting line and build it up from scratch. Now I also want our seniors to look at this new Morning Musume!
--Michishige-san is saying that Morning Musume's true golden era is starting now, right?
Michishige: Being told things like, "During the golden era~" is extremely frustrating. When the current members are singing old songs, we are seen through that lens. I do understand that that is also amazing, though. But still, from the current members' point of view, we also want people to listen to the current songs. When we appear on TV, there have been times when we're still asked to do "LOVE Machine" even though we want to sing songs that we released recently. Of course, we're left with the feeling, "I wish they'd let us sing our current song also, even if just a tiny bit of it." To reduce that frustration, we have no choice but to aim higher, right? So it was with that sentiment that I said, "The golden era is starting now."
tl;dr:
The songs aren't the point, it's the performance.
This isn't the past, so stop pretending it is.
The future is bright and it starts now.