It appears that presently, as of 11/19/20222, that Netlify does not support .NET 7.0 project builds:
Is there a prospective timeline for .NET 7.0 support?
P.S. I am trying to take advantage of some of the new features of Blazor WASM provided in .NET 7.0 (my previous .NET 6.0 build was working just fine in Netlify). I assume I can work around this with a script to install .NET 7.0, but I generally would like to keep that out of my source control if possible.