You say cloud allows massive expansion like it's a negative but it can be boon for a pre-pmf startup or a scaleup. You simply don't have to worry much about capacity planning in cloud and that can be a huge time/effort saver.
Sure, if you're only growing <30% YoY and already paying several millions for cloud and bandwidth/storage are large fraction of that, by staying in cloud you're proving your incompetence as an engineering org.
You say as if every startup scales to facebook size within months. Most startups are hilariously small and their workloads won't stress out a mac mini. Of course, you could overengineer and spend too much and hire too many people, but thats on the people running the startup.
Great, put it on t4g.small or Render or something, what's your point?