I don't know how valid that argument is, because the second time I set up a server was just tweaking two Ansible variable files and running the "provision" command.

Sure, but what I was getting at was parent was just having learn how to use Heroku. And while it's true that automation is something you can do yourself, what about keeping the server up-to-date and patched and so forth? Also, repeating myself here, Lambda et. al. are a step further than Heroku.

There are tradeoffs. You don't have to keep Heroku patched, but you also can't tune it if you need something specific.