'Mirrorless' is a positive in the same sense as 'horseless carriage': it is clear what a piece of unnecessary baggage you are getting rid of.
Even 'compact' is a negative term in an American market that still buys more new F150 'cars' than Corollas.
In evolutionary terms, I am kind of glad that the SL is not particularly compact or cheap, because it helps the new camera form to get over the hump of being seen as only a size or money saver. The SL is saying "I'm going to be so great to look through and so super responsive that you will realize that this actually a better way to do cameras". A kind of myth-buster.