Thanks everyone, some great advice and perspectives here.
Just want to comment on this. If we let them do what they want, they will literally spend 10+ hours a day on youtube/phone. They won't even eat or sleep. This just can't be good. For one thing they both have rapidly worsening eyesight, while I've never needed glasses. I'm not an expert but what possible benefit can hours of youtube have? If they start making money from it that's cool, but that's not happening.
This is a modern problem our parents didn't have. Passive electronic entertainment is like a drug for kids.
@Mr.lover you're absolutely right, we've killed their self esteem. I wish I could give them positivity and encouragement and stop criticizing. But the choices they make are objectively terrible and I'd be dishonest to say anything good about them. We have given them many opportunities to be good at other things - various sports, arts, tutoring, programming lessons. But nothing ever clicked and usually they quit everything.