While I can agree the repetitions are very real, the endless mode is what makes me enjoy OfA much more than iM@S2. The sole reason for that is because you aren't nearly as constricted as you were in iM@S2's linear playthrough, being at often times plentiful room for error if your scheduling isn't up to par in something like a Hyper playthrough. Whereas in OfA? You can take it in stride so everything's that much more free form -- it appeals to me as a sandbox player.
In regards to song count, both games do share the same number of base songs (20). When DLC's thrown in the mix? iM@S2 only has 39, but OfA's beyond healthier at 60+ and counting, what with the catalogs still going. The idea of the recent game lacking in this department is straight-up baffling. We aren't even including guest songs to inflate that mighty number, at that.