Bad sleep advice

My son is 9 months old. When we went for his 6 month appointment I told his pediatrician that he is not sleeping through the night and still getting up two or three times. I am a total pushover so I’ve been feeding him at night (mostly for the bonding). When we went back for his nine month appointment I told her he still isn’t sleeping through the night but I can pat him to sleep without eating if I need to.

Both times she has told us that we need to just let him cry and not even interact with him for three nights in a row in order to get him to stop crying. Essentially she wants us to let him know that we’ve abandoned him at night and he won’t cry if he thinks we won’t come. That feels so cruel. Is there any other advice you’ve gotten that helped you get baby to sleep through the night?