> 10-15 years ago, having a fully baked, first class, slavishly source compatible implementation of GNUstep with broad adoption throughout Linux land would have likely been a game changer.

I think that GNUstep has actually been around since the mid- or late-90s — but it was never a game changer. I don't know why really (was it 'fully-baked' and 'first-class'?), although for my part I just never found a reason to use it.