Both decadence and chronic ailments cut against the human tendency to imagine a crisis as something that either leads to some kind of fatal endgame quickly or else resolves itself and goes away. Being sick for a long period of time has a baffling effect on friends and family and acquaintances, not because they’re unsympathetic or unwilling to help, but because our primary image of sickness is something that comes and quickly leaves, or comes and threatens your life and needs to be treated intensely with the highest stakes — and it’s harder to know how to respond to having something that apparently isn’t life-threatening but also doesn’t go away.
In the same way people analyzing cultural and political conditions are drawn, very naturally, to the sharp alternatives of progress or decline, full cultural health or late-imperial collapse. Indeed they tend to swing back and forth between the two poles, so that often the same people most confident in the arc of history bending inexorably toward liberal progress turn into the deepest here-comes-Hitler pessimists when the arc seems to bend instead in some dark or unexpected direction. So to suggest that there’s actually another category of civilizational condition, one defined by stagnation and repetition over a potentially extended horizon — saying, for instance, that the American republic is decaying and gridlocked and sclerotic but also not yet particularly like Weimar Germany or 1990s Russia, let alone 5th century Rome — is a way of conveying the same kind of truth that’s conveyed by living through a chronic illness, or loving someone who’s living with one: That the drama of human existence is replete with long unhappy interludes that feature neither an immediate Nemesis nor a simple cure, and those interludes require a distinctive response from their inhabitants, neither complacent nor hysterical, but constructive in ways that are intended to bear fruit across a longer haul — years for the individual, decades for society — than the response to an immediate all-or-nothing crisis.
An obsessive focus on the immediate moment is what makes catastrophists and triumphalists; their lack of temporal bandwidth renders them wholly insensible to the incremental.