With these big firms, I just assume they are doing incredible work that can’t show. There are only a couple of firms where I constantly see great work, but maybe that has more to do with their clients wanting to be recognized as supporting design rather than the level of their work.
While a great designer theoretically could design anything, so much of finding a great solution is being passionate about the problem and the space you are working in.
This explains why so many male designers design dildos. Sorry, couldn’t resist.
Seriously though, I think passion is just the fuel to great design. I can design anything, but I know that my first ideas will be only surface deep and lack direction. It’s being driven enough to keep chipping away at the problem and keep trying to increase the understanding of the problem that makes a great design. Sometimes, this is limited by the client (no money or time). Sometimes, it’s limited by the designers ability to work efficiently (burn through the bad ideas fast enough to get to the good ones).