What if sections will be needed now, and it's easy enough to make a plan to eventually connect all of the parts as needed? Get the zoning work done to prevent anything over 2 stories tall being built over the planned route, and then build the various sections as needed/as budget is available. I'm not saying that's what happened, but I can see smart, modular, as-needed infrastructure projects being drawn out over decades like this.

The irony of software engineers complaining about a project not being feature complete and on time.

??? I think you’re thinking of US roads, which are generally shoddily constructed and poorly maintained compared to chinese ones.

No, what you meant to say was “and only 47 people died constructing it!”