Not saying that this is not an issue but there is absolutely nothing Linux can do to make every legacy GPU work without help from Nvidia.
Yes, they can. They literally have the correct (legacy) driver in the Ubuntu repo. But the autoinstaller installs the wrong driver during installing the OS. And if you try to manually install it, there is not even a text prompt in the CLI saying “You just installed that driver, do you want to actually use it to? (Y/n)”.
They could have even gone so far as to make a CLI wizard (like many other packages do) or even a GUI wizard. But no, the package just installs and does nothing by default.
It uses the open source driver out of the box, which works sometimes but not for everything and definitely not for gaming.
Also that is not correct. All the *buntu installers ask you when you install the OS whether you also want to have closed source drivers installed, and then it installs the closed source Nvidia drivers. Just the wrong ones.