If you don’t understand how the OS works at a very fundamental level, you will write sub-optimal code. This is usually fine, because people are smart, compilers are good, and hardware is absurdly fast. However, the fact remains that it’s probably giving up some bits here and there.
More germane to my point, though, the amount of libraries and tooling and abstractions being spun up to avoid having to run a server seems like more effort than its worth. Serverless sometimes has cost merits, but as a counterpoint, you can get a 1 year RI micro EC2 for something like $3/month. If your app is struggling to run on that, either you have the scale to justify more cash outlay, or your app has performance issues – and now we’re full circle back to the previous paragraph.