There are still many interesting companies working on hard problems, real science, and real engineering. Don't get caught up in working for one of the startup darlings just for the name recognition. Go for what interests you and motivates you, and if given the choice between real technology and some kind of rudimentary "app", go for the real tech. You'll learn a lot more and spend a lot less time dealing with product managers, business people and fighting with incompetent co-workers. You became interested in tech because of your love for solving problems and for making things work, so find a place where you can do that.

When evaluating companies I often ask myself what the business would look like before the age of computers -- if we didn't have smart phones and the Internet, what would the business look like? Would I still want to be working there? What is the actual business? In many cases you'll find it's driving people around, cleaning people's houses, or serving as a glorified bulletin board for services. Would you still want to work there if you removed all the tech? Or is the only reason tech is involved is to serve some ancillary purpose to the business?