So the author is saying, don't buy SaaS, that's vendor lock-in. Instead just go all-in on one platform... like Cloudflare, the one (& only) platform that the SDK he writes works on. Which isn't vendor lock-in? No, wait, everything is vendor lock-in:

  No matter what choice you make, it's always going to be vendor-locked in.
  Switching out something, even if it's open source and self-hosted,
  means that you're rewriting a lot of code.

That's not what lock-in means. Just having a vendor-specific component or integration, is not the same thing as being locked-in to a vendor or integration.

Locked-in means that switching it out for something else is either A) impossible, or B) would require an investment greater than just sticking with the existing thing.

When you write software in a loosely-coupled, highly-cohesive way, the intersection between different components is designed to not take much work to replace one component or another. The same is true of systems. If the interfaces of those components are simple, and their use is cohesive, it should not be difficult to replace a part. However, if your components are not cohesive, then it will be a huge pain in the ass to replace anything.

So, no, it's not a good idea to choose a platform because "everything is lock-in, so fuck it, i'll lock myself in even more!" As a developer, I can see the appeal, as it means less work for you. But as a business owner, this is a stupid reason to choose a solution. Choose solutions that will support the business and give it flexibility to change over time.