I think it should be what its founders want it to be:
Spinster is a woman-centric website created to provide a platform for feminist dialogue.
And, as they say, open to men - however they identify - provided they can manage to be respectful towards women.
That said, I looked - and still look - askance at those men who couldn't even bring themselves to wait a few days or a few weeks before barging in. We all know the presence of men affects dynamics and it showed a spectacular lack of self-awareness not to self-exclude until the women had settled in and created the ambience they wanted.
The forming, storming, norming, and performing process for that site should belong to women. I've taken note of those men who were blind to that and I will remember.
I've enjoyed my first days on Spinster immensely and I've found loads of new and wonderful women, with some of whom I share particular interests (eg social class). I might have missed some of them if I'd been busy saying hello to blokes I like.
So for me, and me only: I'm determined to create an initially female only space and set of interactions there. All the men I come across - even the ones I like - are being muted/blocked. I will reassess at a later date when I've got things going how I want them and the ambience going how I want it and do some unblocking.
But for now and for me: woman only. Quite how following and interacting with a wide variety of women of different interests and views is creating an echo chamber is entirely beyond me. It sounds more like anti-feminism to assume it would be any such thing.