....what the hell are you talking about.
Any PCIe based graphics card will work in any motherboard with a PCIe slot, no matter if it's 1.0, 2.0, 3.0, has a traditional BIOS or UEFI, etc etc etc. Some boards may have specific, odd, and rare compatibility issues with specific cards, but I don't know of a single example off the top of my head. Yes, performance may be somewhat degraded, but if it's a full 16x slot with all lanes available even PCIe 1.0 is enough for all but the fastest cards, and if it's in a board that old you're probably CPU limited anyway.
Either I misunderstood your claim, or you're flat out making shit up.
New cards in the last 2 gens need a motherboard that has or can support uefi bios. This is the same problem I had with my workstation motherboard by supermicro which was made in 2009, I could not upgrade past the 7xxx line from AMD or the 6xx line from nV, because from that point on all videos cards started only using UEFI bios, the only card I could find that I was going to use a stop gap was a 750 ti by MSI which had dual bios one for uefi and one for legacy, even when it was set to legacy it didn't work, when I called up MSI they stated the specific motherboard I had need a legacy bios update, of course the last bios update was in 2012 for that motherboard and so that wasn't going to happen.