The issue is really with the business model of most IOT device makers. They sell you one device once and they're basically committing themselves to running cloud services for that device indefinitely. This only works while you're growing, and when sales start to plateau you're suddenly paying huge amounts of money to maintain the infrastructure with no money coming in.

Companies like Google, Apple and Amazon are big enough to absorb that, but the smaller ones will quickly start looking at ads and subscription fees.

It would be a lot better if device makers could just stick to building the hardware, after which the user just plugs it into their IOT provider of choice (which would be a subscription or something self hosted like Home Assistant).