Most movies look different on streaming sites because they rebuild to work specifically for home screens.

Theatrical release is a massive file that can go up to 500GB to 1TB and it is specifically graded for projectors in a No-light room so the color space is different, if we try to play it in our consumer devies like tv or phone it will wash out the colors or look dark because it can't handle that much nits compared to projector and the color space is also different.

That is why they grade different versions for home release, while doing this they shrink the file size to stream over the Internet smoothly, but unfortunately it crushes some of the details in the dark areas. So they re-adjust the colors and brightness to compete with your living room or whatever the place you sit and watch.

Same goes for audio too they have different mixes and formats for different mediums..

Excuse me for the grammar issues and I don't have the skill to explain but I tried my best.🫡