These 3 know where there bread is buttered and want to honor the group that made them who they are today and I see nothing wrong with that.
If people think it's basic and tragic then they simply don't have to engage.
Surely the big show booked for next year will see, at the very least, Mel C rejoin them so I don't see the harm in these 3 doing something they WANT to do while the other 2 keep trying to distance themselves further from their legacy which ironically only serves to tie them closer to it.
People seem to want to write this off as an instant failure but nostalgia, especially for something as big as Spice Mania, shouldn't be underestimated.
New material is also probably a very smart move to focus on the members who want to be in the group and what they can bring.
Happy endings are just stories that haven't finished yet...