in a game that only exists on pc developers can aim at high-end pcs, and make graphic options that can reduce the performance necessary. Everything is fine.
in a game that was first on pc, then went to consoles (diablo 3 for example), the second version is dumbed down and graphics are reduced, effects removed. Everything is fine.
In a game that is first on consoles then comes to pc, or that was developed for consoles even if the pc version comes out at the same time...
Well many things can happen. In bad ports, the maximum graphics and effects the devs make are what the consoles can handle. if you have a computer that is 4 times more powerful, well too bad the game won't look better. Several games have this "ultra on pc = consoles" problem.
It's not just graphics that is a problem in ports. Diablo 3's controls were changed from pc->console (no targeted abilities because no mouse), there are less monsters (performance problems), screen is smaller (performance again). In a bad port, console->pc controls and limitations remain there and it's stupid that happens.
This is not really the fault of consoles, but more of a money problem. the devs could make the pc version much better. but that costs money. making a new version of the game almost from scratch (I don't know a lot about development, but it definitely costs) is an investment that has to be done because consoles exist. Yes, I criticise the game companies that don't invest on the pc version and release a buggy, limited, frame-capped, dumbed down version of the game.
But I'll also critise that consoles are making gaming overall worse. Not just pc gaming. This generation is objectively worse than last generation when compared to the hardware improvements that happened over the years.
Ps3 was so good, pc enthusiasts bought it and installed windows on it. I know professors on my university that did that (computer science). this generation has hardware from 2012. it's a joke and a cash grab.