The whole thing could've run on a single low end VM and used RDS for the database. Using a more standard framework, it would've been cheaper, faster, and easier to maintain.
Serverless can be done right, but it's rare...
sure, that OS patch was auto updated, but that vuln in our deps that showed up over the weekend did suck in our time.
We lost productivity, the cloud credits ran out and so did our good folks.
For example, if scaling various parts of your application independently is a hard requirement, you're going to want to follow some set of these practices. Otherwise you're probably not going to see any practical benefits relative to the additional complexity.
However, Serverless has its flaws. I wrote a post a while back where I talk about the current landscape. It's a bit out of date, but if there's interest I might update it and post it here.
When life hands you executives with zero accountability, make lemonade I suppose.