I have a full 200 gig icloud drive filled with photos and when I got my 2016 macbook earlier this year it took a couple weeks for it to finally finish processin

I have a full 200 gig icloud drive filled with photos and when I got my 2016 macbook earlier this year it took a couple weeks for it to finally finish processing everything. Here I thought the point of having all the images in the cloud was so the devices didn't have to process all the images every time you re-install/get a new device. Is it really too much to ask for photos to simply pull images only on demand and not try to download as much as it can if there's space available? This laptop is supposed to have an "all day battery" but in reality I only get 5-6 hours of fairly lightweight usage.