Golgoth is a weird module in that it doesn't add any additional feature expect what's available in the modules it packages. So it's fair to wonder "what's the point?". This page should answer those questions.

Won't this drastically increase my bundle size for libraries I don't need?

Yes, it will. golgoth is not meant to be used for browser code. It should be used for CLI or backend code, where you don't really care about the disk footprint.

I could manually add the modules I want when I want them, what's the point?

See golgoth as a protyping tool. Install it to bootstrap a project with every library you will most likely need. If you feel it's too much and you're barely using one or two libraries, remove it and replace it with the one you actually need.