To suggest a 6 ton titanium engine that slams into a concrete slab is going to leave it perfectly intact is absurd.
I'm afraid you seem to have very little awareness of how aircraft are constructed. You describe the engine as though it's a solid block of titanium. It's far from being so. A high-bypass turbofan consists of a traditional roughly cylindrical/tubular-shaped turbojet engine, encased in a larger shell which contains the large-diameter fan on the front, and allows the air to flow around the central engine unit:
The inner engine is made of myriad small aluminium, magnesium and titanium parts - discs, blades, chambers and pipes - few massive castings or forgings (the discs are probably the most substantial parts and ooh look, there's one in your picture!). All are made as light as possible, and in themselves are very strong. But as a cohesive unit, an airliner engine is not the monolithic block you make it out to be.
Titanium, as Dave pointed out, is used in limited areas, where its properties are required. It's expensive stuff, and not needed everywhere. The outer casing is even less robust than the main engine - it's made mostly of sheet aluminium and carbon fibre skins, with the air-flow space between it and the central engine. As such there is a great deal of space for the casing to crush and deform into - damage easily inflicted in an impact like this. Given the shallow angle of impact, the concrete foundations would likely suffer little more than scrapes as the wing passes over it, whilst the outer engine would be crushed and torn away, the remainder of the engine continuing into the rest of the building with the other remains of the plane, sustaining more damage as it goes.
Think of your car, crashing into a wall (let's all consider that for a moment). It's not a block of metal; it can compress, deform, crush, to a great extent and in even low-speed accidents.
Does that help?