x100 What am I doing wrong?

Nobody, not Fuji, Nikon, Canon, Pentax, or Sony is going to be able to make a camera that is smarter than YOU, the human operator (I know there are some close calls, to the human race's shame, not the engineer's brillance)... no matter how you meter it, using averaging, spot, or matrix, you still must ask yourself several questions:  1. what is the most important element in the shot?  It's a big dark auditorium, but let me tell you, if you were the conductor or a musian on stage, you'd be able to read fine print in an investment prospectus... they put that much light on the performers! You should realize that. Look not at the whole scene, but at the performers, who I suspect were the main point of the shot... like a rock band on stage, they have great light... so expose for that.  If you could walk up an meter the performers on stage, you probably would have gotten something in the range of F 5.6 @ 1/80 sec at ISO 800!!!  Now you just have to ask yourself, "how much of the architecture do I want to record as well..." then you make tradeoffs (how much can I blow out the stage to record details in the dark hall?)  and that is where your phone camera excelled... its "dumb" metering system could not brilliantly outthink itself to create bad expsoures like your Fuji and your brain!

As I have said before: "sometimes you have to turn off the autopilot and fly the plane yourself!"

* God's greatest achievement? -- the human brain is still the most complex computer ever created, it weighs less than most laptops, is assembled in a wet, dark, bumping assembly space only large enough to fit into the hips of a woman, and is assembled by un-trained staff in just a few months.

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Holding a camera, any camera, reduces my blood pressure, calms my nerves, and gives me a sense of opportunity!