I agree with you, Photos has serious problems and iPhoto was a better product. Photos worked pretty well for me until my MacBook Pro suggested that I change preferences for photos to be stored in full mode in the cloud because the computer no longer had room for them. At that point is when I should have saved my photos to a hard drive instead of in the cloud. I set preferences on my computer and on my devices to allow that. My problem with the "Closing the library" sign started because I wanted to get the full resolutions of photos and movies onto an external hard drive and it was taking hours to download them a few at a time or even one at a time. I wanted to be able to download a lot of photos from the cloud to an external drive, but when I changed preferences again, it started downloading the entire library in the full resolution mode to my computer. There is no way to download photos from the cloud to an external drive without them first downloading full res to your computer. Then I got the message that I must go back to the preferences and save the photos full resolution in the cloud when the library on the computer was full. So I did that. I now get that message and it has been days and it hasn't finished. Photos won't quit or allow me to restart the computer. I am afraid to try to force quit because Force Quit Applications does not show that it is not responding.
Apple should create a way for users to download photos from the cloud onto an external hard drive without downloading the entire library to Photos first. It should also allow you to select certain photos from the cloud and download them to an external drive without downloading first to Photos. Right now, for me the problem is not so much Photos as it is how my photos disappear into the cloud at full resolution but to get them back, especially movies, it takes a very long time and causes problems.
Users cannot log on to their icloud account and see their photos while logged on there and select photos from there to download. You have to do it from the Photos app on the computer and devices. I would like to be able to see them and download the ones I want from my icloud account quickly.