I am not going to argue with you about specific technology or use cases. But these are complex pieces of software, and the fact that you consider them to be "boring technology" is the reason why I was talking about "extremely boring technology".

When you are building software really fast, you need to take the boringness to the next level and cut all non-essential components.

At fly.io, hosted Redis costs over $100/month, when one server + Postgres is less than $10/month. This tells you about the complexity.

Many people use Redis with Django, because that is "obvious choice" for Celery. But either Django built-in tasking (or backport with django-tasks) allows you to handle most of the use cases (long-running tasks, timed events) when combined with a cron such as Superchronic.

Many people consider ElasticSearch as an "obvious choice" to handle full-text search, but Postgres can handle it in most cases.

Mostly, if you have problems that require "webscale solutions", then you will have a team building a dedicated solution anyway.