> Hasn't the ISO to install W11 now gotten too large to be burned to the biggest DVD?
No.
The Windows 11 media creation tool still officially supports creating a DVD installer from ISO image for Windows 11 (including the latest 25H2 release), alongside USB drives etc. The requirements for the DVD version are still the same 8gb of space it has been for a while. As of today, the ISO is 7.2GB.
Virtually everyone uses a bootable USB thumbdrive or similar today though, and page you download the ISO from heavily encourages this, and is trivial to make with the Installation Media tool Microsoft give you.
Could be a small number of experienced users, a few thousand in every city, who have always installed Windows from optical disk.
Reliably and simply using the ISO as intended for it's primary purpose of being burned to optical disk.
Moving from CDROM to DVD to large DVD would have been the rarely-triggered optical-drive upgrading cycle driven by Windows bloat alone.
Looks like Blu-rays would be the only thing big enough now.