I'd say it isn't irresponsible at all. You've got to do what you need to do to look after your own mental health. One thing I am utterly sick of is the shaming of anyone that breaks "the rules" that seems to have become normalised. Especially when it comes from people who have families and partners at home.
We seem to be obsessed with the idea that you could be somehow responsible for someone's death if they get infected via you, even after several degrees of separation. I guess this idea has some logic to it, but it's such a departure from how we think about things normally.
By the same logic, many of us have probably helped to "kill" a few elderly/vulnerable people in the past by passing on the influenza virus.
I'm not saying we shouldn't all take sensible precautions, like isolating when you have symptoms and hand washing etc. But this shaming needs to stop.
This is arguably a little irresponsible of me; I have a housemate who is a social worker and not isolating, which makes me a potential link in a transmission chain. But on the other hand, we're spending nearly zero time together in shared spaces (we literally go weeks w/o seeing each other) and I'm very conscientious about what I touch and when in shared spaces. And delivery or random passers-by on walks are my only other form of exposure, so it seems like a managed risk if not absolutely minimized.
I think some who live alone are going to find this kind of quaran-team approach important as we break past the first few miles of the marathon. The trick may be in really doing it thoughtfully in a planned-out conscientious manner rather than waiting until arriving at some breaking point and throwing caution to the wind.