I have a cousin who uses a wheelchair, it seems unfortunate, but now they have a wide variety of formats to meet specific needs for their users, so it's not as bad.
My brother, who died in 1998, used a wheelchair that was heavy and hard to use.  Today, you are right, there are many more lightweight options.
I'm sorry to hear about your loss. Yes they are lightweight now and have specialized seating adaptions, individualized controls, and other features to help efficiency and ease of use.
Are there any that are aluminum and foldable?
I don't know for sure, but I would certainly imagine so. I know they even have ones specific for activities like sports wheelchairs, so I'm sure aluminum foldable ones exist.
Right now I'm looking for an aluminum and foldable wheelchair ramp for my mother.  Everything related to wheelchairs take up a lot of space.
Wheelchair ramp
A wheelchair ramp is an inclined plane installed in addition to or instead of stairs. Ramps permit wheelchair users, as well as people pushing strollers, carts, or other wheeled objects, to more easily access a building.
A wheelchair ramp can be permanent, semi-permanent or portable. Permanent ramps are designed to be bolted or otherwise attached in place. Semi-permanent ramps rest on top of the ground or concrete pad and are commonly used for the short term. Permanent and semi-permanent ramps
Wheelchair
A wheelchair is a chair with wheels, used when walking is difficult or impossible due to illness, injury, or disability. Wheelchairs come in a wide variety of formats to meet the specific needs of their users. They may include specialized seating adaptions, individualized controls, and may be specific to particular activities, as seen with sports wheelchairs and beach wheelchairs. The most widely recognised distinction is between powered wheelchairs ("powerchairs"), where propulsion is provided by batteries and electric motors, and manually propelled wheelchairs,