Comedians blame the crowd. It is usually the geometry.

A crowd laughs when it hears itself laughing. A high ceiling, soft furnishings or seats spread across a wide room all absorb that feedback, and a joke that would have built dies after the first few people. Packing a small audience into the front half is not a seating preference, it is acoustics.
Anything physical needs everyone to see it. In a room with a pillar, low stage or scattered tables, visual material is a gamble and verbal material is not — which quietly shapes the acts that develop in a given venue's regular night.
Close, and you can be conversational: pauses work, small reactions read, shouting feels aggressive. Further back, that same delivery disappears and the act has to be pushed. Many performers have one setting and wonder why alternate weeks go badly.
A room where the audience is lit and the performer is not inverts the usual dynamic and makes everything harder. If a venue will change one thing, ask for a light on the stage rather than a better microphone.
Arriving early and standing where the back row will sit answers more questions than any conversation with the promoter. You find out whether the mic is needed at all, whether the bar is audible, and where the dead patch is — and all three change the set.