Well, not necessarily. This past year, I have used my 35mm Summilux (with a M6) in Gothic cathedrals, on dull, overcast days, without tripod or flash, at fairly normal speeds (30/60/125) and the pictures came out flawlessly.
Moreover, I find that I can photograph indoors in natural light without flash, and the pictures (of, say, my mother) come out perfectly.
In fact, I bought the camera and lenses precisely for the challenging situation of dark, light deprived northern Europe in the half of the year when natural light is often awful.
The camera is light, (as in exceedingly portable), reassuringly solid in the hand, and the 'fast' lenses are extraordinarily forgiving. (That is why I bought them). I didn't want a massive doorstopper of a camera.
Now, I will readily grant I won't get action shots - but, to be honest, that is not what interests me.