Why are the 3d shapes in my older projects compressed?

Hello, this is a major issue I have when opening up my older projects.

Unfortunately, almost very 3d shapes are flattened and compressed. why did it happen and is there another way to fix this?

Older projects can look squished because 3D shape objects now use their own Z height property, and the default may not match what the old project expected. Check the Z height on those shapes first, and compare the layer or camera settings too, since the 3D update changed how some defaults work. If you can, make a copy of the project and set the Z height by hand on one shape to see if that fixes it.

The project may be affected by the removal of the legacy Z axis scale 'Normalized'. See the corresponding section in Deprecated features for more information.