My understanding is that the labor was primarily provided by non-slave populace during the periods where their labor was more available (i.e., neither harvest nor planting season). Would you as a pharaoh want your eternal resting place and it's associated grandeur built and installed by the adoring public who think you're literally a manifestation of a god on earth, or by slaves who probably don't accept your deity and will share the secrets of your tomb with grave robbers?

This aside, yes, there is a distinct difference between things built in the past (the circumstances of which cannot be changed, irrespective of modern observation) and things built in the present by (modern day) slaves for current use.