If the aerator cleanse solves the problem in the kitchen and the bathroom but not the shower, there may be other easy fixes for the shower.
The vacuum breaker (backflow preventer) associated with the shower wand can fail. I can't speak to all models, but in mine it is easily accessible at the shower wall, inside the shower compartment. Remove it and re-connect the shower hose with no vacuum breaker. If that results in a satisfactory flow, replace the vacuum breaker. They're readily available on Amazon. If no improvement, re-install the original.
It may also be that crystals are clogging the shower head. There's no easy clean, replace the shower wand.
Another shower problem possibility is that the most commonly used shower head requires more water volume than typically passes through the pressure reducer/flow reducer. My solution to the latter situation was to replace the shower wand with an Oxygenics head. It magically gives the illusion of greater flow.