Possible answer, maybe.
Suppose that the Universal expansion has ALWAYS been accelerating. It began when the Universe itself began. Then, the Universe began expanding very slowly and has gradually been accelerating. Now, this makes the Universe VERY old, perhaps more than a trilllion years. There is plenty of time for the background radiation to have become isotropic without any "inflation". The "missing matter" is just the very old galaxies that have burned out and are no longer visible. Of course, this in no way explains the accelerating expansion itself.