If the OP wants to insist upon a full refund, that is their right. But I don't think this comes anywhere the standard for a full refund and the proposed compensation sounds fair enough to me.

This wasn't a St Regis, it was a Residence Inn. And it's not just Marriott, I would expect to see bathrooms like that at any Holiday Inn Express, Hampton Inn, Hyatt Place, Best Western, etc. that hadn't been renovated in awhile...