First of all, science is trying to better understand the world, by making models predicting something. It isn't engineering.
Engineers don't just apply known science, they deal with the parts of the system that aren't obeying the textbook rules and find places to look for new phenomena in the process. To do so they analyse behavior and build models that predict the tolerances needed to get things working with a high degree of confidence. The difference is they don't go off on tangents because they have an objective, but engineers are often the initial discoverers of phenomena. It usually takes a pure scientist to then go in to spend the time explain more precisely why they had to make the tweaks they did, but there is plenty of overlap and there are plenty of people you cannot put into one category or another.
most of the basic ideas in (mechanical) engineering are pretty much settled since Newton got hit by the apple
Um, no, mechanical engineering has more to deal with now than they did then, because materials science and nanotech are increasingly important components.
I don't know where you get your ideas about the engineering disciplines. They pretty much all have frontiers.