I used a bad example with the Date API, except that, say, using moment or date-fns and sticking to it would be better than jumbling them up. If you’re going to do a migration from one to the other then it has to be committed to.

Dependencies themselves can’t be good or bad. They only acquire that property in the context of the dependent codebase. And a codebase that you can’t spin up from scratch or easily grok because of its approach (or lack thereof) to dependencies is almost certainly on the bad end of the spectrum.

I’ve seen this destroy some python codebases internally. In fact, my choice of a JS example was unfair because it becomes an absolute shitshow in python once you have dependencies and transitive dependencies with very tight version constraints.