If you read the entire passage, God restricts any who are part of the family that were priest who have certain deformities from being able to offer the sacrifices in the tabernacle/temple. This included deformed backs, limbs, etc. That is because it was hard, heavy work to butcher cows and left them about four and a half feet to the top of the alter for sacrifice. People with deformities like that would have been unable to do such work.
So God excused them from having to do that work, But he stated that they were still to receive the same amount of pay/food as those who worked at the alter. And they were permitted to do other jobs that a priest would not normally be able to do.
If you think it is heartless to assure that disabled people are taken care of, feed, etc the same as everyone else, I have to wonder if it is actually you, and not God, who is heartless.