If you use cloud brand queue system, you not only need to run some servers to run the queue, you also need to rewrite all parts of the system that relied on cloud brand queue system into something else.

Repeat it by a bunch of cloud services your app use and you're in for major rewrite.

Cloud offers many, many "good enough" solutions for common problems in development and it is oh so easy to use another cloud api for few cents more

And that's not even touching a bunch of auxiliary services you now need to provide like monitoring, backups, metrics etc.

Usually best strategy is to start move from most expensive parts but if that part is entangled in cloud services it could take forever