I'm not sure I agree with some of the examples... For instance, since Redis can replace Memcached in addition to other chores, what would it have taken for a migration strategy to eliminate an older tech in favor of the newer one?
In the end, I understand how each tech adds costs and values... however, one shouldn't be afraid to update/change things. It's too easy to be stuck on a decade and a half old tech if you are and don't at least try to keep up a little. Then the upgrade is exponentially more costly.
I don’t think the point is not to migrate. The point is to discuss and make the decisions globally not at the whim of “this makes me happy” or “we have a new problem”.
In the end, I understand how each tech adds costs and values... however, one shouldn't be afraid to update/change things. It's too easy to be stuck on a decade and a half old tech if you are and don't at least try to keep up a little. Then the upgrade is exponentially more costly.