Everything Apple has done since iOS was first introduced (or arguably the initial iPad support in iOS 3.2 ) has been incremental improvements. But drag and drop is one of the bigger ones, IMO on-par with the initial multitasking support which incidentally was the update that finally convinced me to buy an iPad.
For an example of where this smooths things out, I've been using Readdle's Documents as an approximation of a local filesystem for a while now. Saving an image to that before was tricky; iOS doesn't have a way to isolate an image out of a page, just copy or save to camera roll. So you could save to camera roll and then import it over, but you lose the filename in the process and replace it with something generic like "Image 10". Or you can do weird workarounds like using Workflow's "Get images from page", which pulls up a slideshow of all the images on the page, which you then get to scroll through and find the one you wanted.
Now you just drag it and put it straight into the destination. You can also drag the URL bar over, which saves the URL as a new text file.
And if I have data in Documents that I want to use elsewhere, there's no shenanigans required with piping it through share sheets, I just drag it out and use it.
If you want something less permanent than a file manager, the popover multitasking is also a good platform for temporary "shelf" style data buckets. I'm currently trying Scrawl Pouch, but I've seen a couple others that looked equally nice. It's basically intended as a drag-and-drop destination to temporarily store any type of data until you want to drag it back out somewhere else.
This can be the obvious stuff like images and links from Safari, PDFs and other files out of Documents. You can also drop things like map pins, which can be shared via messages or email or dropped as links into Pages documents. I haven't experimented a lot with 3rd party apps, but presumably we'll see this show up in other ecosystems, maybe dropping things like audio effects between a family of media creation tools, or someone could make a 3rd party service for sharing paintbrush presets that you could drop into Procreate.
They've also brought in the "spring-loaded folders" behavior from Finder for this. If you're dragging a URL and you want to add it as a Safari bookmark, you can hover it over the sidebar button to pop it open and then navigate to the folder where you want to drop and save it. Or after the sidebar opens, you can hover over the Reading List tab to put it there instead of bookmarks. It's integrated like that throughout the entire OS.
A whole lot of things that just weren't possible on iOS are now a 2-second interaction.