I'm frankly surprised some proper standard didn't pop up already, I guess closing the users in your own ecosystem as fast as possible is priority in the industry.

Good 80-90% of devices could be just "an MQTT connection + a bit of code to pair it up initially and feed server data" + a bunch of templates for how typical services should present themselves (so a light will just work with any compatible "control center"). Then just sell user subscription to your cloudy cloud IFTTT clone or a separate box to put in house that does the same job.