Ecommerce software is about as close to okay at it as I have seen, but still vendor driven and still full of idiosyncracies. I can at least create a product in a PIM and it pipes through to all the places it needs to go once it is set up.
(Come to think of it, I have a spare VPS, maybe it's time to try out Huginn.)
RE Alexa, call me a whiner, but "Alexa, ask $BrandApp to XYX" ruins the immersion a lot :(.
Ultimately, the problem is control. On-line services control both your data and how you work with it - from the flow of actions to UI[0]. An interoperable world requires vendors to give up a lot of that control.
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[0] - They control the entire experience. As if they were a fucking Disneyland, not just a hammer, from users' point of view.
SaaS has no such option. It either does every little thing you need, or it doesn't solve the problem.