What games did you work on (or kinds of games, if that's too personally identifiable), if I may ask? I'd be curious what sort of games have so many objects flying around that the overhead of vtables and cache misses was a significant factor in your overall performance.
I worked in the industry myself for a year or so, on an MMO (back when they were the Next Big Thing) and while our game wasn't super optimized, OOP overhead wasn't even on our radar as an issue compared with rendering, wrangling art assets, Scaleform UI elements, dynamic loading of the same, and all the other bits and bobs.
(Not arguing that composition isn't often better, just that performance isn't usually a significant reason why.)
I worked in the industry myself for a year or so, on an MMO (back when they were the Next Big Thing) and while our game wasn't super optimized, OOP overhead wasn't even on our radar as an issue compared with rendering, wrangling art assets, Scaleform UI elements, dynamic loading of the same, and all the other bits and bobs.
(Not arguing that composition isn't often better, just that performance isn't usually a significant reason why.)