It should be an expectation that a more modern game is superior to an older title, not just graphically but in terms of mechanics and content.
Games like Back 4 Blood simply highlight that outside of a higher minimum level of graphical fidelity games are quite simple worse beneath it.
Their not the only one, and for younger gamers this won't be a problem because there is no comparison point for them, but for older gamers you can easily notice the slide back in quality compared to prior titles.
It shouldn't be acceptable, but it is.