My deployments to Lambda are extremely simple. All I do is hit save in VSCode and the Lambda is updated. Change the env to prod and it deploys instantly to prod.

There's tools that make it easy, I'm still using a tool I built 10 years ago. Very little has changed except the addition of layers, which are also pretty easy and automatically handled in my dev tool.

All the Lambdas I write also run locally, and testing isn't an issue.

The only gripe I have with Lambda is when they deprecate older nodejs versions, and I am forced to update some of my Lambdas to run on current nodejs, which then leads to refactoring due to node module incompatibilities in some specific situations. But those are really nodejs problems and not so much Lambda problems, and it does get me to keep my apps updated.

YMMV.