According to Eli Dourado, the original interpretation of the NEPA law was reasonable. The earliest Environmental Impact Statements (EIS) were often less than ten pages. Afterward, through a combination of district court decisions and the decisions of the Council on Environmental Quality the work required to create an EIS ballooned to make it unreasonably expensive to comply with the EIS requirements.

It's noteworthy that neither laws passed by congress nor court decisions by the Supreme court are responsible in the growth of the work.

Whenever cases reached the Supreme Court, the court usually ruled against expansive interpretations of NEPA. Zachary Green describes the court decisions in his master thesis "NEPA in the Supreme Court:  A history of defeat" by saying:

Since its enactment in 1970, the National Environmental Policy Act (NEPA) has been the focus of seventeen Supreme Court cases. Government and industry have defeated environmental organizations in each of those seventeen cases.

In United States v. Students Challenging Regulatory Agency Procedures the Supreme Court argued:

But 694*694 nowhere, either in the legislative history or the statutory language, is there any indication that Congress intended to restore to the federal courts the power temporarily to suspend railroad rates, a power that had been clearly taken away by § 15 (7) of the Interstate Commerce Act.

The statutory language, in fact, indicates that NEPA was not intended to repeal by implication any other statute.

This is a clear statement against an overreaching reading of NEPA. Given this history of Supreme Court cases, it seems to me that there's a lot of room for the Supreme Court to rule against the current interpretation of NEPA without having to rule against any precedent. Given the current trend of ruling very pro-business, the current court would likely be even more willing than past courts to rule against expansive interpretations NEPA.

This year the Supreme Court decided that the EPA overreached when they decided to regulate CO2. In the process they created precedent that reduces the amount of freedom agencies have to just do what they want.

One argument might be to say that the Council on Environmental Quality overreaches the authority that congress has given it?