Same here. But, I assume you have managed PostgreSQL in the past. I have. There are a large number of people software devs who have not. For them, it is not a low complexity task. And I can understand that.
I am a software dev for our small org and I run the servers and services we need. I use ansible and terraform to automate as much as I can. And recently I have added LLMs to the mix. If something goes wrong, I ask Claude to use the ansible and terraform skills that I created for it, to find out what is going on. It is surprisingly good at this. Similarly I use LLMs to create new services or change configuration on existing ones. I review the changes before they are applied, but this process greatly simplifies service management.
I'd say needing to read the documentation for the first time is what bumps it up from low complexity to medium. And then at medium you should still do it if there's a significant cost difference.
I think if it were true that the tuning is easier if you run the infrastructure yourself, then this would be a good point. But in my experience, this isn't the case for a couple reasons. First of all, the majority of tuning wins (indexes, etc.) are not on the infrastructure side, so it's not a big win to run it yourself. But then also, the professionals working at a managed DB vendor are better at doing the kind of tuning that is useful on the infra side.
With a managed solution, all of that is amortized into your monthly payment, and you're sharing the cost of it across all the customers of the provider of the managed offering.
Personally, I would rather focus on things that are in or at least closer to the core competency of our business, and hire out this kind of thing.
this part is actually scariest, since there are like 10 different 3rd party solutions of unknown stability and maintanability.