Can grad school admission recommendation letters be generic for all applications?
Recommendation letters generally do not need to be tailored for each school. Admissions committee members are faculty too, and in an age where people regularly apply to 10+ programs they understand the undue burden this would place on already busy faculty.

Occasionally a more tailored letter may have some advantages, for example if the recommender has close connections at one of the programs, but it is definitely not expected or required.