For example, I am more of the "All you need is Postgres" kind of software engineer. But reading all those fancy blog posts on how some team at Discord works with 1 trillion messages with Cassandra and ScyllaDB makes me envious.
Also, it seems that to be hired by such employers you need to prove that you already have such experience, which is a bit of a catch-22 situation.
In other words, the developers you're envious of didn't start with Cassandra and ScyllaDB, they started with the problem of too many messages. That's not an architectural choice, that's product success.
This varies by domain of course, but non-postgres solutions are generally built for very specific problems – they're worse than postgres at everything except one or two cases.
Overengineering is more prevalent the more money a company makes and companies who overengineers will pay good money to keep the overengineering working.
Unfortunately the rest of the executive has leaned on them so hard about AI boosting productivity they aren’t able to avoid thst becoming a mess
Some of it is consequence of managing so many individual contributors, I still believe a lot of companies use microservice stuff as a way to scale to more teams than to more scalability/reliability/observability.
Some of it is just people coming up with clever solutions (and leaving after the fact) and a lot from resume-driven development.