Someone who doesn't seem to react — who is always "taking a pass" in the conversation of life can be described as impassive.

Impassive is tricky, as it sounds it should be the opposite of passive. It's not, though. The fact is you can be passive and impassive at the same time. When a passive person gets passed over for a promotion at work, their face might remain impassive upon hearing the news.

Definitions of impassive

adj having or revealing little emotion or sensibility; not easily aroused or excited

“her impassive remoteness”
“"he remained impassive, showing neither interest in nor concern for our plight"- Nordhoff & Hall”
unsusceptible to or destitute of or showing no emotion

adj deliberately impassive in manner

deadpan, expressionless, poker-faced, unexpressive
incommunicative, uncommunicative
not inclined to talk or give information or express opinions

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