It is not memory that makes a being aware, and it could be argued that memories serve to detract from awareness of the moment, so I question whether a being without memory would be in any way "dumbed down". There would be indifference to impermanence, but not necessarily any decrease in awareness.
And there would still be suffering based on unpleasant sensations.
True, memory does not necessarily make a sentient being aware, meaning; cognitive processes continue to function in the absence of the ability to retain memory. However there would be no retention of cognitive information and therefore one's condition would be no different than that of a newborn infant. Hence why working with individuals who suffer from dementia is essentially equivalent to working with a child.
'Dumbed down' is appropriate in this case because this scenario would be equivalent to simply functioning in the causal ālaya, with no hope of acquiring the type of insight needed to be liberated from a predicament of that nature.
Now on the other hand, if the individual is able to cut through memory via direct insight into its emptiness, that is a different story. In that case the influence of memory would be pacified through prajñā, and that species of insight would most likely collapse the ālaya, inducing a freedom from the delusory reference point maintained by memory and imputing ignorance. Quite the opposite of the 'dumbed down' abiding in the limited, karmically influenced structure of mind.