As you get older cranial bones become more fixed and less able to move.
If you want allow these to move then try holographic breathing. This creates a natural form of mewing and starts a craniofacial breathing motion that continually adjusts the bones of the face and cranium so they can slowly move into a new position over a period of time.

Holographic breathing produces a natural form of mewing.

The tongue naturally starts suckling to the roof of the mouth. In holographic breathing this is done in a very relaxed way and over a period of time the tongue releases its toxins and stress and then naturally suckles to the whole roof of the mouth and stays there.

Holographic breathing also heals craniofacial dystrophy –

Holographic breathing also creates a craniofacial breathing motion where all of the bones of the skull and tongue are opening and closing with the breath.

So in holographic breathing you're not trying to get the face and cranium into an end position. In holographic breathing, the whole face cranium and tongue breathe and this naturally starts bringing it back to a more natural position. The tongue after a while being fully on the roof of the mouth does the same as mewing but more because it is breathing and moving. The videos to learn holographic breathing are free. If you like mewing my guess is that you'll love holographic breathing.

I have free videos on this and a free webinar today all on this link – https://www.holographic-breathing.com/1/index.php/free-webinars-meditations