You probably “saturated” the USB bus...it is probably much quicker to copy the old external drive to the new laptop internal hard disk, then copy from the new laptop internal HD to the new external hard drive.
“USB 4” & “Thunderbolt 5”(newest Macs) are the newest/fastest external interfaces (much faster than USB 3.2).
Every version of Windows has larger overhead/more bloat...so your new i9/Win11 machine will probably be about as fast as your old i7/Win7 machine. (unless you “debloat” it):
https://christitus.com/windows-tool/
i have 2 thunderbolt 5 ports on my intel MB- but nothing on the market yet will really utilize it- just a cable for it is $40- but it is backwards compatible - so still pretty limited to 20GB/s for now- but that is still way faster than what i had before with HDD’s and usb2
The thunderbolt 5 is supposed to be 120 GB/s- now that would be nice!