I wish more people would send things via `Share iCloud link` instead of just sending media directly. I usually try to do that. I finally fee like this feature is pretty good at photo sharing, works well and bug free. The way it works is you select what media you want to share over iMessage (even >1k works succesfuly for me), and Apple then gives you link which when a recipient visits, they can directly add to their iCloud, seems like it's a backend-to-backend copy, since even very large transfers worked quickly like this for me. And the benefit is that it doesn't use up iMessage space (just iCloud photos space).