You have to compare the 5,1 with what else was available at the time. Was NVME storage even available in 2010…It's hard to sell me (and presumably others too, hence the post) on a Mac whose own stock I/O is so outdated that you have to buy a PCIe SSD to make up for the difference. Though inter-compatibility on PCIe cards between MacPro5,1 and MacPro7,1 (and presumably Mac14,8 too) is a nice touch.
A Radeon RX6900XT wasn’t even built back then but the 2010 Mac Pro can be upgraded with both and with newer wifi and Bluetooth so it remains useful.
If Apple is to bring on GPU driver updates then we should be fine for 7000 series AMD GPUs in our 7,1 machines.
Otherwise we just use windows and install whatever we want.