Kind of a no-win situation. Cloth interiors which were "Fingerhutted" when new had pristine looking seats for years. When the plastic was removed, the "pristine" fabric had dry-rotted and quickly disintegrated.
Even without the plastic, the aging of the cloth fabric will continue. Put a little strain on it, or even a cardboard box in the back seat and the fabric and the foam under it can tear.
IF the cloth is still in good condition, probably best to learn how to get into the car without any squirming around, which can put stress on the fabric. Rather than entering the driver's seat by sitting and turning, figure out how to step into the front floorboard, then continue to sit down pretty much where you'll end up. If you need to adjust your position, raise up to do it rather than sliding/squirming around on the seat. When you exit, put your left foot out first, then pivot on it as you raise up out of the seat.
Blankets or bath sheet towels can work, IF they are properly anchored over the seat bottom. Sliding around would still be discouraged, though. Higher thread count sheets can work, too.
Just like not pushing down on the armrest as you open the door can take some awareness of what you're doing (AND putting more wear into the door hinge pin bushings!), these things can take a little time to learn. But once learned, they become second nature, by observation.f
See what works best in your situation.
CBOd'Y67