I have a hard time thinking of a game in which some aspect of game design was cut to keep a steady 60 fps. Graphics? happens all the time, but design?
Well poly count could be one thing (reduced enemy count for example) and lighting could also be a thing that could affect gameplay to a lesser extent (in certain genres like stealth & horror). I remember seeing Carmack (before the release of Rage iirc) talking about how hard was the decision to go for 60fps and how many other devs inside Id disagreed with that because of how it affected the game design.
So yeah targetting 60fps is not easy and it almost always means hard work that doesn't translate into praise or satisfaction from the consumers, especially the last few years where a game can get ripped to pieces for a sub-HD framebuffer or other graphical hitches (see CoD & Id tech 5's megatextures) and 60fps are rarely appreciated (was the reason why Insomniac stopped making R&C 60fps) it's not strange that most devs target 30fps and call it a day.