A bad behaving dependency (has useless deps) doesn’t invalidates the whole idea of using a package manager.
Probably the author has not enough experience in maintaining projects written by smart people where they write by themselves all the collateral parts.
Using dependencies extends the “standard” library so that it increases global (extra team, oss) reuse and the probabilty to find something “known“ in your next project.
Could be wrong, in that case I’ll stand corrected.