This show deals with the nature of the self, and so I feel a slightly professional interest in it, aside from its entertainment value (considerable!). It's very high-concept premise: a corporation develops a neural implant that splits a person into separate selves, one for the workplace, another for the outside world, and they switch automatically as they enter or leave the office. The selves can't communicate with each other and have no cognizance of the other's experience.
The corporation, Lumon, is ultra-creepy and obviously up to no good, although the exact nature of what their aims are remains a mystery. There's a Reddit forum with a ton of elaborate theories, but I'm not too interested in that, it will be revealed or not in the course of time.
It's more interesting as metaphor. It's kind of obviously about the actualities of "work/life balance", but it also seems to be saying something about the more general way in which we construct different personae for different situations, and ways in which they interact (or don't).
It's pretty normal to have different aspects, but if they are too independent it is either pathological or simply deceptive insincerity, and in extreme form can be sociopathic manipulation. Work in particular requires us to present in a certain way, to express certain aspects of ourselves and leave others at home. I don't even know if this is such a horrible thing, it's just how society works, we perform different versions of ourselves in different contexts. It can be oppressive but that's how mature adults operate, only naive teens think they should be able to be authentic all the time.
But what it really is an exaggerated cartoon version of Marx's theory of alienation. The worker's situation is not just that they have to act in a certain way, it's that they are being robbed of their real agency, trading it in for meaningless but economically remunerative "work". It's not just a different context, it's a context with a radical power imbalance.
It reminds me of Counterpart, another show that played around with multiple and split identity, although in a completely different idiom. Counterpart is ultra-realist, shot on location in a grimy Berlin, and aside from the conceit of two split worlds, everything is as normal as can be, at least, normal for a spy thriller. Severence on the other hand exaggerates every visual element, the corporate office is cartoonishly bland, like some archtype of an office settting with no extraneous detail, everything clearly planned by some evil visionary.
Also the visual style is has strong echoes of Vivarium (2019) – the bland white and green surfaces, lack of details and texture, and the monotonous repetition; as well as the more thematic similarities of people trapped in a relentless and all-encompassing mechanism of alienation.