I used to handwave cloud portability. Turns out when you're shipping things and need extra services and you have deadlines, you build against the platform. I think the GP comment was probably expressing wariness of the free cloudflare tier that entices you to build against their APIs and their product shape in a way that inevitably locks you in. Sure, you could migrate, but that's expensive.
Yeah, good point. For a little hobbyist site of no importance, I'm not too worried about vendor lock-in, but that calculus changes as it gets more important.
That's the catch though. By time you're scaling, there's tension between roadway and revenue and headcount and it's the worst worst possible time to need to reachitect.