It's not the pcie5 bit that's a problem. It's that it has only 8 pcie lanes (aka pcie5 x8). Pcie doubles its bandwidth each generation so pcie x8 is equal to pcie4 x16 but because the card only has 8 lanes available, if a motherboard's primary pcie slot is limited to pcie4 x16, the card will still only use 8 lanes of pcie but at pcie 4 speeds, cutting its available bandwidth in half.

That said, while it does come at a slight performance cost, the bandwidth available even on pcie 3 motherboards is sufficient to be virtually indistinguishable while in-game. Going from a pcie 5 x8 connection to a pcie 3 x8 connection on a 5060 ti will generally only result in a loss of framerate of about 1-2% .

It's a bit cheap of Nvidia to not put a x16 bus on the card regardless, but generally the "it's only x8" criticism is pretty overblown.