However big crazy engineering projects require money which is been sunk into dumb social purchases instead.I can imagine it killing internal engineering morale also.

Why does any of this making working at Yahoo as an engineer even a little more exciting?

All we've seen so far is external projects get big money and attention. Where's the internal projects that would make working for Yahoo exciting?

Right now I'd rather be working for a company that planned to compete with Yahoo.

Yahoo unlike google doesn't gives that much freedom to engineers to work on their own ideas. Engineers can't make much difference, if same managers who are not doing much now are present. Some major revamp of workforce starting with managers is needed.