Gimp stats may mean less when you have a group (or large group), but that kind of forces everyone to rely on the group rather than themselves
You say that as if it was a bad thing.
...especially when your stat generation methods force everyone to have a gimp stat.
Pray tell, which stat generation method is that?
Most heroic fantasy tales do not center around a group of 4-6 characters but around one alpha (fe)male character and some others tagging along or dropping in and out to provide support. Dragonlance and some Forgotten Realms books are the exception to this, but that's because they are based around a game, not the other way around.
And the lesson we should draw from this is?
"Average" doesn't mean "gimp", so if your players all have at least average stats, then they should be able to face just about any challenge with a fair chance of success whether they are alone or with allies.
Seriously? Errr... could you reread that and tell me what it means, because to be honest, I don't understand what you are trying to say and the levels on which I find that to not make sense are as multi-tiered as a Dallas interstate exchange.
You should be able to run a game of all fighters or all wizards or all rogues and allow them a chance to succeed.
Possibly. I'm not sure that that is the case, but let's for a moment concede that your statement is true even if it flies in the face of decades of RPG experience. Supposing it is to be true, whether or not a group of all fighters and or all wizards or whatever succeeds or fails, or can expect to succeed or fail most certainly won't have anything to do with their stat distribution. The success or failure of an unbalanced party won't be over whether they have high stats, but will certainly hinge on whether there is some expected class ability or function that the designers expect to be present but which is absent in the party. It has nothing to do with the topic at hand at all. For one thing, it's quite possible to imagine a party of all fighters where one is playing 'the strong fighter', another 'the agile fighter', a third 'the tough fighter', and a fourth 'the smart fighter'.
Gimping a stat just to make a character "interesting" or "realistic" just doesn't make the game as fun.
I know that any internet statement should always be appended mentally with 'in my own opinion', but sometimes even when you are mentally appending a statement with that, it's actual absence from the page is still so glaring that you feel compelled to point it out anyway.