People overthink these things and get riled up over less than nothing. This is common sense and good for all.
Shades up for landing in case of emergency. Being able to see what's outside helps to orient people in an emergency and may also stop them from using a particular exit.
Shades down on off-loading helps to keep the aircraft cool. It's a minor ask for a major benefit for the next passengers.
Staff can certainly do this, but that takes time and time both costs money in terms of staff and also means that turn time is extended (and perhaps if done by cabin crew may extend their mandatory rest period).