SLR was a technology to enable viewing the subject through the lens when another kind of eyefinder with a through-the-lens view was not possible.
Now it is: you can have a digital viewfinder that shows the same through-the-lens captured image.
I'd say for photography, it's beyond what most would care about anyway, you can go shoot 300-400 pictures all day and not have to recharge. And if you need to shoot longer, you could carry a pound or less battery in your pocket.
The weight will be offset by the much smaller weights of mirrorless cameras and mirrorless camera lenses - as the former don't need to carry a prism mechanism, and the latter can be made smaller and closer to the sensor area.
EDIT: but for the title question, I'm also not particularly keen on buying a DSLR instead...