The energy requirements for running modern civilization aren't just a scalar number--we need large amounts of highly concentrated energy, and an infrastructure for distributing it cheaply. The normal economics of substitution don't work for energy.

A "tradeoff" exists between using resources (including energy and material inputs of fossil origin) to feed the growth of material production (industry and agriculture) and to support the economy’s structural transformation.

As the substitution of renewable for nonrenewable (primarily fossil) energy continues, nature exerts resistance at some point; the scale limit begins to bind. Either economic growth or transition must halt. Both alternatives lead to severe disequilibrium. The first because increased pauperization and the apparent irreducibility of income differentials would endanger social peace. Also, since an economic order built on competition among private firms cannot exist without expansion, the free enterprise system would flounder.

The second alternative is equally untenable because the depletion of nonrenewable resources, proceeding along a rising marginal cost curve or, equivalently, along a descending Energy Return on Energy Invested (EROI) schedule, increases production costs across the entire spectrum of activities. Supply curves shift upwards.

It's entirely possible that failure to create a superintelligence before the average EROI drops too low for sustainment would render us unable to create one for long enough to render other existential risks inevitabilities.