I worked at a few small shops that initially used Heroku. The story in all of them was the same: Heroku is nice and simple to start with the free/lower plans,

I worked at a few small shops that initially used Heroku. The story in all of them was the same: Heroku is nice and simple to start with the free/lower plans, but gets too expensive as you grow a bit more. Once we'd grown past the free/lower plans, we'd move on to somewhere else, that required a bit more work, but was substantially cheaper and way more flexible. Also an issue was a reproducible environment for several devs. Using docker became super easy, but this didn't translate well into Heroku. We either needed to maintain buildpacks and dockerfiles in sync, or move to a platform where we ran docker. Not sure if this has changed since, but this was also a big reason to move elsewhere.