Does anyone really know what mainstream model agencies look for?

When you say you have applied to 'thousands of model agencies', were these real agencies, real professional ones, or the thousands of scam 'modelling academies' who will tell everyone they are 'stunning' and then ask for money... money for pictures, money for lessons. etc etc...? If you were model material, and you applied to REAL agencies, you would have been signed up by now, so I think you have to look at another career.

Have you gone to open calls at any of the agencies you've applied to, if they have them? That's your chance to ask them to be VERY honest with you about why you are not getting signed. Maybe one eye is bigger than the other, maybe your nose looks funny in pictures, maybe your neck is not long enough, maybe you are slightly knock-kneed or you have poor posture. There is no way to know. Just because someone is stunning doesn't mean they will be a model Lots of models are not stunning, many of them are odd looking

Agences don't look for one specific feature or type of look. What they look for is -- "Will one of our big clients want to book this person on a job?" That's it. If their big clients are Vogue Magazine and Gucci, then they look at a model and ask themselves if this is the type of model Vogue or Gucci will book. If their big clients are more mainstream companies like Gap or J Crew, they ask themselves the same question

But the only way to really know is to go to open calls when agencies have them and ask them to be very honest with you and not hold anything back. You might not like what you hear, some can be brutally honest, but at least you'll know and stop wondering why

So there must be some reason why you keep getting rejected by every agency, including smaller ones.