Because this project uses pinned dependency versions, it's very likely that consumers will end up with multiple versions of various dependencies like React. React doesn't like to have multiple versions, and in some cases this is causing me problems.

I think it would be better to use semver and specify only the minimum required versions, and allow proper dependency resolution. You can check in a package.lock or yarn.lock file to ensure that consistent versions are used during development, if you like. But I don't think it's a good idea to pin dependencies as you have in your package.json.