The bottom right thumbnail thing really bugged me and confused me when it came out, because I always just want the screenshot on the desktop right away, as it used to be. I don't know why they couldn't have the delay/thumbnail AND put the file somewhere I could reach it immediately. But IIRC, there is some setting that disables the thumbnail behavior and lets the file be written instantly.

Funny, I never want the screenshot saved to a file and I literally never look at the desktop. I either use ctrl to store the screenshot in the clipboard or want to use marker tools and then copy the clipboard. This new flow was an improvement to me.

I use a trackpad exclusively with MacOS. If I want it immediately on the desktop then I can just "swipe away" (to the right) the thumbnail and it skips the pause.

Not perfect but I do value being able to edit it from there, or right click and save to clipboard. So it works for me.

For me I want it to hang around longer actually. I will take the screenshot I want, open up mail or messages or something to dump it there. Right as my mouse is hovered over it and a milisecond before I can click it, it jumps away. I've resorted to sometimes giving it a partial drag which resets the counter while I am still getting situated over to wherever the screenshot is going.