SUSE
MOBILITY IS BEING ABLE TO MOVE FUNCTIONALLY AND EFFICIENTLY WITH LITTLE TO NO RESTRICTIONS OR LIMITATIONS, ESPECIALLY AROUND YOUR JOINTS.
Unlike flexibility; which is passive, mobility is muscle strength, range of motion and endurance capacity.
To improve your mobility you will need to have healthy and improved joint function. This could mean swapping too much passive (inactive) stretching with a more solid strength foundation.
My favourite example is, while standing up, if you use someone else, or a wall, to lift your leg forcibly up to your head; that is impressive but it is a passive range and ultimately quite useless functionally. However, if you can stand upright and, with strength of your hip flexors (as the main muscle), bring your leg up to your ear with no help - that is productive and has more long term benefits with the joint than passive flexibility ever will.
My tip to you is to use your muscles actively and dynamically to improve your mobility; ultimately improving your flexibility and joint function at the same time.

@coach_suse