But then, having also lived it, upgrading to newer versions of PHP and it's required modules is also not trivial.

And it's often not just your language, the cloud vendors have a lot of incentives to get you to use their hosted Postgres, or AuroraDB, or GameLift. Or even something as simple as we built all of our deployment scripts/images for our PHP system on Amazon Linux X, and now for reason Y, only Amazon Linux X+2 is supported.