These complaints make me laugh. Stardust has always been the limiting resource. Nothing new. Now they are giving us more top level mons (tier 3/4/5 raids with elite IV) and TM to help make more mons viable again. Therefore there is more to power up.
Also, as people get to a higher level, power ups cost more.
Nothing is new. All that has changed is less people go hunting for wild pokemon now. That is how you collect stardust, same as it has always been. It's not like they suddenly dropped the stardust available. There is a little less from gyms and a little more from catches (evolved forms give a small boost).