When forced to use AWS I only use the extra features I am specifically told to or that are already in use in order to make the system less tied to AWS and easier for me to manage (I am not an AWS specialist so its easier for me to just run stuff like I would on any server or VPS). I particularly dislike RDS (of things I have used). I like Lightsail because its reasonably priced and very like just getting a VPS.

S3 is something of an exception, but it does not tie you down (everyone provides block storage now, and you can use S3 even if everything else is somewhere else) for me if storing lots of large files that are not accessed very much (so egress fees are low).