If it were what it claims to be on the tin, maybe it could work. Care for yourself. Take time to visit your doctor for regular check-ups. Address health issues as they crop up. Be willing to spend money on your health. Exercise regularly and practice preventative routines to keep yourself in good order.
But self-care on twatter isn't anything like that. It's people jerking themselves off over how amazing they think they are. People who claim to have low self-esteem are spending all day on social media humble (and not so humble) bragging to strangers about how they're fucking awesome. Now, I don't know about you, but I've never met someone who holds a low opinion of themselves, who suffers from anxiety and depression, who also spends all day on social media bragging about being great. I've encountered plenty of narcs who do that shit though.