It's at tops, a 15-30 second wait
First: it can be a lot longer than 15-30s. One project I work on takes around 90s for a fresh install. This used to be worse in older versions of npm, and it's worse on Windows.
Second: it also affects things like CI/CD. I prefer using Yarn 2+ for that reason (all dependencies are stored as part of your repo). It might not sound like much, but 30 extra seconds does decrease your productivity more than you might think if you have to wait for it every single time.