Increasing Returns

Not exactly sure what the question is suggesting.

The fact that ideas are nonrival points to aggregate increasing returns to scale in the production of goods (not in technical change)

I am not sure this is just due to ideas being non-rival.

Key idea in modern economics

The premise is OK but the inference seems too vaguely sweeping...

For motivation, see the brilliant document provided by the prize committee! :-) IRS also requires at least CRS in non-idea inputs.

Non-rivalry gives rise to increasing returns to scale; most ideas are non-rival (unless protected) and central to technological change.

Ideas can be protected, and imitation is costly, but the statement is broadly correct, with huge implications for R&D and antitrust policy
-see background information here
-see background information here

Ideas are non-rival hence do not get constant returns to scale at macro-level because standard replication argument breaks down.
-see background information here

Assuming the question means increasing returns in production of output (as distinct from production of new technologies)

Nonrivalry of ideas is important for growth and means there are positive externalities to research. Does not have to mean economy-wide IRS.