Hi Dear,
Welcome to Health Care Magic Team.
Understanding your concern.
New crown of last molar tooth as you said is lower in position which means this crown is not at all in occulsal contact with teeth of opposite jaw. If teeth are not in proper occlusal contact while chewing it will cause load to distribute unevenly which in turn cause pressure on muscles and temporomandibular joints and it will cause wasting of muscles.
Your tooth can be saved easily that is not an issue but what your need is removal of existing crown and resetting it to higher level. A well fitted crown will allow you to bite proper once it is properly inserted.
Resin cements along with bonding agents are used now a days for crown lengthening.
Subgingival i.e below your gum line margin placement can be done to improve height of your crown.
Alternation of tooth preparation design with placement of retention forms can be done.
I would suggest you to stick to your exiting
dentist and tell him your problem because if you will switch to another dentist that could be very costly for you and new dentist can cause same mistake again.
Hope your concern has been resolved.
Best Wishes,
Dr. Harry Maheshwari