That’s Not Invented Here syndrome, and it’s decidedly bad advice.

The cost of dependency management may be understated but it’s always less than the cost of reimplementing everything found in established libraries.

One HTTP connection per message (if this is what the original poster meant) is probably a bad idea whether you implement it yourself or not.

Also, let's be honest: The phalanx of developers that violently argue for importing everything and never implementing anything yourselves is way bigger than people who argue for the opposite; I don't think we need to worry about the latter making things worse as much as the former.

We've seen what the world turns into in both scenarios, I would argue, and at least with the first one we got software that ran decently and developers who knew how to actually do things. We have overall much safer languages now so their home grown solutions won't have the same safety issues that they've historically had.

With the importer crowd we've gotten software that feels like molasses and an industry full of people who know only the surface of everything and more importantly become tied to frameworks and specific APIs because they never actually go beyond any surface APIs.

As with most tradeoffs in software there is a good middle-ground, but we won't ever get there if we don't have people who argue for making things yourselves.

Who has the time to count the cost. Just keep shipping and worry about the costs later is the reality in a large portion of the tech ecosystem.

Being judicious in which dependencies you take on is not the same as Not Invented Here syndrome. Code is usually a liability, not an asset.