Exactly right, just the pure fact that it's at your disposal makes you think about problems in a whole new way. For example, I recently just abstracted my solutions away from Redis. I have nothing against redis however removing a dependency makes things more simple, which is important for my setup.
For caching you have SO many options which are already built in, ets, agent, ets + gen_server, or even reaching out for a library like nebulex.
Another example is recurring jobs, you can create a gen_server that will run a job every x hours in roughly 50-100 lines of code depending on how complex your problem is.
I rarely feel the need to reach out for external dependencies. Not that there is anything wrong with that, it's just that you now have a wider array of tools to work with and some problems are just solvable with a couple of lines of code instead of having to reach out for external tooling.
I recently built a distributed work queue, generally in Ruby I would use something like sidekiq, however elixir made me feel like "hey you can write your own" which generally is not recommended since you don't want to re-invent the wheel, but if you are doing something that breaks away from the existing solution, having the ability to craft a custom solution that works for your specific set of problems is extremely powerful, you can get much more creative, and the important thing is it got done fast (I wrote a distributed job scheduler in 2 weeks + 1 week to clean it up and work out the kinks, it's already running stably in production)
