But how much "alphabet" is there still left, other than Google and YouTube? In hindsight it almost seems as if alphabet was deliberately set up as a pasture for the various doomed "moonshots" to die more quietly, with less impact on the main brand.

What moonshot--at least that is known about--is possibly transformative at Alphabet/Google scale? Waymo seems increasingly unlikely both in terms of time-scale and differentiation in a crowded field. And what else is there?

Waymo is very far ahead of the competition. It may be hard to compare given all the fly-by-night competitors but it has had many more years in development and the result is more dependable.

Loon could have made them the ISP for the developing world.

The founders retired in all but name only almost 10 years ago.