Sigh, I typed a reply and lost it. Here's a quick precis:
I'm not struggling with any concepts to do with gender. I seek out other views both online and IRL and I'm confident in my own position.
No, my struggle was simply understanding the linguistic distinction you are making between Not Viable and Not Worth Doing. If there's any echo chamber involved it's the one that comes from decades in business where something judged Not Viable is definitely Not Worth Doing 😂
But!
Since my lost post I realised why we are missing each others' point!
It's an interesting demonstration of the logical concepts of Necessary and Sufficient.
In logic, A is Necessary for B if B can't be true unless A is true. A is Sufficient for B if A being true means be B must also be true.
So, in this case Viability is (usually) Necessary for something to be Worth Doing. However, it's not Sufficient. Something could be Viable but not Worth Doing, for example because something else is more urgent, or will generate more benefit. Which indeed is what you were asserting from the dictionary definition - Viable and Worth Doing are not the same thing.
However, your original argument was that making the WI female-only again was Not Viable, ie you were arguing a negative case.
An interesting feature of formal logic is that relationships don't hold the same way when we look at the inverse. If A is Necessary but not Sufficient for B, we cannot conclude we have B just because we have A. However we can conclude that if A is not true, B also cannot be true.
So in your original argument, when you assert that a female-only WI is Not Viable (because in your view female-only requires not just no males in principle and 99% of the time in practice, but guaranteed 100% no males at any time with no risk of deliberate male deception, and so sorry to the many women(female) who'd be more than happy with the former and accept those limitations but them's the breaks and what can we do?), you are implicitly saying making the WI female only again is Not Worth Doing, and that is the statement people were disputing.
Now, I'm obviously not suggesting that posters who disagreed with you were consciously applying these formal logic rules! But the meanings are baked into our language and generally we apply them instinctively. Just sometimes it's helpful to apply that formal framework to see where the disconnect is.
(I think I've met you before under another username...I do enjoy a chance to brush off the old logic training so thank you. Probably less fun for the rest of the posters 😳 )