Consider an average web dev from that period, who may be working professionally but in small-scale operations, and not in big corp settings.
After reeling from the shock of the pandemic worldwide, they need to make themselves relevant for most web development work in 2020. Automated build and deploy is now as bread and butter skill today as spinning up a LAMP stack was 12 years ago.
If you were to show a web developer from that time period what cloud and serverless products are, and how they can be used, how should you explain it to them? And what resources would be the best for them to learn considering what they may already know?
You're probably going to want to learn about containerization and Docker unless you want to go higher-level with services like Vercel or Netlify (both in the same kind of space as Heroku). The service offerings on AWS, GCP and Azure are worth taking a look at too to get a grounding for what's out there.
Most cloud providers have a fair amount of overlap in what they offer but they've each got their own versions of services with their own quirks. Whatever you choose to dig into, you're best off picking one provider's platform to learn and understand in more detail before seeing how those concepts translate to other providers - otherwise there's just too much ground to cover.
Although most new services and tools are vendor specific, the fundamental ideas have largely converged so don't feel too overwhelmed. At the end of the day, it all still just boils down to VMs managed by someone else.