The 4000 nits are the brightness of the display in the viewfinder. If you enlarge it, it gets darker. A high peak brightness would be wonderful for seeing bright lights in the viewfinder though. It does not look good if highlights are blown out.
I hardly do burst and although my camera has live view, I hardly ever use it either. I hate the idea that the sensor is warmed up even while you are composing, while a DSLR sensor is just powered for a fraction of a second during the exposure. It seem like a waste of sensor time for me, if 99.9% of the time the image from the sensor is just generated to show it in the EVF.
Those cameras focus too much on sport, people and action. If you do not care about those areas of photography, the negatives of a mirrorless camera weigh much more.
I have serious doubts about the durability of mirrorless cameras. Will they really survive ten or twenty years? There is so much new stuff that could break. The IBIS for example. It is a nice feature, but probably the first thing to break.