One of the key challenges we observe is that if you're small enough, a Heroku like experience works well - and most of your needs would be covered by virtually any combination of techstacks.
It gets significantly more challenging when you grow, either in feature complexity or scale complexity - and then very few services can offer what AWS/GCP/Azure offer - albeit at the increased engineering/monetary cost of using them.
We're building a different kind of approach[0] that aims to absorb the mechanical cost of using public cloud capabilities (that are proven to scale) without hiding it altogether.