Most applications are certainly not staffed by large teams, but the advantages would be best seen in large codebases. Most solo developers are working on much smaller TypeScript codebases, and won't experience many issues with the build system.

TypeScript is the main language that I program in every day, and I don't see the advantages of this proposal outweighing the disadvantages.

I would think the opposite. Solo devs are in the most flexible state and they don't care if they need to go through a bit of inconvenience for a slight boon to code quality but say you got several average devs who can only be taught on how to do these things, it gets annoying to set it all up and make sure nothing breaks or you'll be wasting time babysitting their environment.