Presumably you need some functionality in the dependencies that you use. If you don't use a package manager then your options are:

* Import the dependency manually. This is taking a dependency without the formal description a package manager gives you, making it harder to audit, update etc.

* Write the functionality yourself. This guarantees you are not exposed to malicious code, but it takes time and your solution will likely have more bugs than a widely used solution. You also lose the ability to use other dependencies that build on top (e.g. React components) because you are now outside the mainstream.

What is actually needed is better tooling to analyze and prune dependency graphs.