Think about components you rely on for your service. How long would it take you to stand up or migrate to an alternative. Consider that you've also got all your other business to do too. You can't spent a year just spinning your wheels from a business perspective, while you're migrating stuff between services because your upstream provider decided to stop building something. You've still got to keep growing. If you're lucky, you've got staffing for meeting your business growth needs, but odds are that's barely true.
On top of having to migrate, what are your replacement's performance characteristics? Are you replacing it with your own solution instead, and if so how do you operate it, what happens under load, how do you ensure durability? etc. etc. lots and lots of questions and you've got scant 12 months to figure out what you're doing and how to get off it _on top of your existing business needs_.
This criticism has been brought up so many times, and yet routinely we still see GCP saying "but we promise to give you a whole year's notice!" as if that's a good thing.
(disclaimer: I work for another cloud provider)