I predicted at the time that people would take away the wrong conclusion—"dependencies are bad"—from the left-pad incident. Sadly that prediction seems to have come true.
The more dependencies you have, the more likely you are to get one that's going to cause a problem down the line, be it due to conflicts with other libraries, subtle bugs that take years to manifest, or someone deleting something from upstream package manager (as was the case with left-pad).
Take crypto code. Which do you trust: a homebrew implementation of AES-GCM because nobody wanted to add a dependency, or libsodium?
However, I think the reason that people got upset over the left-pad thing was because it was a library that most engineers could write fairly easily, without adding in another failure point.
If you rely on the the language/platform's built-in libraries, typically the amount of wheel-reinventing you are doing boils down to writing simple wrappers, without adding in another external point of failure. These libraries are typically more production-hardened than something you'd find on NPM or Maven or Nuget.
Leftpad was a problem with a particular package management system, not with code reuse. It's true that avoiding code reuse is a way to avoid package management problems, but it's kind of like the way decapitation is a way of avoiding mental health problems.
What I mainly took away from the left-pad incident was that if people will add dependencies for code that is so simple that it takes less than a minute to write(1), then what else will they add dependencies for? I was a bit surprised at the sheer poor engineering judgement involved in adding massive amounts of dependencies so carelessly when they were so fragile as they proved to be in NPM.
Raise your hands those who check all dependencies before every release? Did you look at all the change logs? Did you check for issues, security vulnerabilities, or that it may be time to upgrade to a newer version (or not)? Did you follow all the transitive dependencies and do the same? Do you routinely evaluate each dependency with an eye to replacing it? No? Yes?
Using known good implementations that you know to be maintained, is good. Overdoing creates new problems. Making a culture of it creates a community of fragile, ratty code.
Dependencies are bad if you overdo them because with scale problems tend to morph into new kinds of problems.
(1) You usually do not need to do all of what left-pad does. Usually you need one specific case. And once you have done it a few times (for a few different cases), it becomes like a kata you can write in seconds. It is much faster than adding a dependency. Not least because adding a dependency actually means you should spend enough time reviewing the dependency - in depth the first time, and perhaps just checking the change logs or commit logs on subsequent versions.
As with most things - it is a trade-off.