The Campaign Placement Exclusions List is probably a feature I have used the least in my time working on Google Ads, probably because I do less display than search and the benefit of this particular tool is when you are doing multiple display campaigns.
If you have a display campaign running and have spent countless hours excluding sites you don’t want to advertise on, you certainly don’t want to go through it all again, or multiple times due to multiple campaigns.
The solution for this would be this video, if you simply make a list of sites you don’t want your ads to appear on, you can apply the lists to multiple display campaigns at any one time. This may be even more relevant if you are using display select for your search campaigns as you can also use this tool for display select.