doesn't have to be masturbation. plenty of people are addicted to sex with strangers or other types of coping mechanisms.
sex is problematic because it's it's seeking a short term high. like drugs, gambling, junk food etc. all of these mess with your brain and create lead to mal-adaptive brain chemistry. being high/chasing high isn't what happiness is.
amen. seeking fulfillment in others is the surefire way to be miserable. the most miserable people I have known were the ones who entirely derived their worth from others approval, and often it was so bad they had no internal validation mechanisms and often very poor internal regulation and they were seeking someone external to do their regulation for them.