How best to proceed cleaning this or is it a loss cause?

I visited an old relative and was rather shocked at the state of their Le Creuset. They clearly don't or have never given much attention to cleaning it and clearly burn their food and use too high a heat.

I gave it a good scrub and it made no difference.

I'm wondering what might shift the black off to give a better outward appearance?

Bicarbonate of soda? Any and all advice gladly received. Thank you all in advance.