Kafka et al definitely have their place, but I think most people would be much better off reaching for a simpler queue system (or for some things, just using Postgres) unless you really need the advanced features.
* Lack of interest for other team members, which translated to doing what they thought was a sufficiently minimal amount of knowledge transfer
* An (unwise) attitude that "it's already set up and configured, and terraformed, so we can just acquire that knowledge if and when it's needed"
* Kafka guy left a lot faster than anybody really expected, not leaving much time and practically no documentation
* The rest of the team was already overwhelmed with other responsiblities and didn't have much bandwidth available
* Nobody wanted to be the person/people that ended up "owning" it, so there was a reverse incentive
Postgres is the solution in question of the article because I simply assume the majority of companies will start with Postgres as their first piece of infra. And it is often the case. If not - MySQL, SQLite, whatever. Just optimize for the thing you know, and see if it can handle your use case (often you'll be surprised)