Is it permissible to be content with merely disapproving of evil in one's heart upon seeing wrongdoings on social media, focusing solely on oneself, while advising only those among relatives and friends who accept advice?

Denouncing evil is a collective obligation (fard kifaya); it may become an individual obligation for a person, and its obligation is waived in certain situations, including: fear of harm, or the widespread nature of the evil and the occurrence of extreme hardship in denouncing it, or the lack of responsiveness from the one committing the evil. It is permissible to suffice with denouncing evil in the heart when others are undertaking it or when there is a reason that waives the obligation.