Ironically, I'm still largely about idempotent calls that should be able to trigger something. And those idempotent identifiers can be stored such that you can replay or serve up the relevant data, as needed. But going all in and forcing a long compute chain that cannot be changed is something you do in places you have to do it. No reason to choose to do it everywhere. And certainly don't build larger and larger compute chains between durable writes to the backing data store.
I don't see any reason whatsoever that a temporal workflow composed of activities would be subject to the things you've described. And I don't even think it's that impressive of an implementation of the idea.
My complaint was less that it isn't a compelling idea. The problem seems to be that people want to expand the one system they are working on to be a fully comprehensive system. I remember one team tried to get their entire state reflected in a Step Function state machine that could run for as long as necessary. Idea literally being a state machine that would last years or so. They compromised for one that would only last a week or so. And then faced the consequences rather quickly.
And note, given enough time, I think this can work. On a deadline, though, I've seen it fail too many times for it to be my goto solution. All the time by people that are objectively smarter than I am.
(obviously the rules are different for KV/object/blob-stores and don't apply here).
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That said, if you need a stopgap solution for a problem like that, then take advantage of existing compatibility-shim features in a decent RDBMS: things like VIEWs and SYNONOYMs exist for this reason (and yes, you can INSERT INTO-a-VIEW).
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Another option is to constrain your DB designs such that all DDL/schema changes are always backwards-compatible (i.e. disallow dropping anything, disallow alter-column except to widen an existing column (e.g. int-to-bigint is okay but not string-to-UUID), all domain-model attributes must be initially modelled with a m:m multiplicity whereever possible, etc etc) - and you can enforce these rules using a DDL trigger too - and any changes made by a workflow's DML can be repaired by a background job.
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(Just throwing some ideas around)
Would be keen for a python implementation
