One reason this is tricky to do is because up until let's say the last 6 months or so, myQ _wasn't_ hostile, even if it was Cloud-based. (I get that that aligns with your point! I'm not arguing with you there.)
The company could go out of business and shut down their servers. Or shut down the servers because they're no longer selling the product.
Sometimes incompetence is as bad or worse than malice. The company could break an API accidentally. Or the API only works intermittently. Or they could add poorly-implemented rate limiting that unintentionally affects multiple users when they share an IP via NAT.
What matters is that they provide proper documentation for their APIs, encourage devs to use them, and don't have a history of breaking old clients with new firmware updates (without very good security reasons).
But in general, OK - some things are better done via an on-line service. But it's the minority of cases - almost none of IoT devices have a legitimate reason to route control and diagnostics through the cloud.