It's definitely worthwhile to learn Lambda, S3 and serverless apps but all that stuff can be learned on the job. S3 is especially easy to use for most use-cases and any decent programmer can learn to use it in an hour or two.

However, I would definitely learn a SQL dialect and learn how RDBMSes such as Postgres work (especially what is meant by ACID) as most companies are based around a database. Don't believe the hype - SQL is not dead. Dynamo is a great technology but there are many problems it can't solve for you.

Finally, I personally don't know Azure or GCP so well. Only knowing AWS in-depth hasn't held me back so far. I've used a few of Azure's services but I've never built a serious app on it.

My recommendation is to not really worry about individual technologies and to focus on safely handling and working with data.