You say Apple has almost none, yet is doing great. So what? Lots of things that were or are shit have done well. Even things that are now illegal. Do you like discrimination?
Every company the size of Apple should have people of all backgrounds, ages, sex, race. For every room full of twenty somethings designing a "great" product achieving ridiculous financial results there will be a dozen features or possibilities missed to invisibly cater better for more groups (potential customers).
Perhaps they need to use it in subtly different ways, or have different goals that needs an option or overlay not seen by the room full of bros. Perhaps when you hit 50 and your eyesight isn't quite so sharp so you need reading specs before you reach for the phone you realise Apple's much vaunted, industry leading, accessibility is shit. A few 40 year olds on all the teams might have noticed that and come up with better ideas and solutions than the current dross.
As to diversity being a drawback in execution, what utter twaddle.