Unnecessary points of failure
It is actually easier to design and implement a home automation system that does not rely upon "cloud" services than it is to do so with all the extra remote bollocks on distant servers. There is no fundamental reason why the logic needs to be hosted in the "cloud" or that you should need to pay any kind of subscription for this. None of the back-end processing requires anything approaching server-level power.
• Secure, dumb-ish devices connected to your home LAN? No problem.
• A coordinating system (effectively a computer requiring no more power than an RPi) which orchestrates activity by said devices? No problem: it's the size of a paperback and cheap as chips.
• A secure connection through your router so that you can password-connect to your coordinating system from office, phone, tablet, whatever? Pitifully simple. (Logically, you might build the coordinating system into a router, even.)
Or: reliance on a third party's "cloud", trusting that it won't go down; be hacked; hike its prices; steal your data; open your house to intruders; distribute pictures of your sleeping children; sell your privacy for a shilling to the entire world? No thanks.
If your home internet goes down, you're out of luck anyway. But why introduce an additional point of failure, so that everything goes horribly wrong because a server in the Pacific Northwest breaks, even though your own internet is fine and dandy?
In any event, the word "ecosystem" is converging closely with "prison".
When companies try to steer you into dependence on their ecosystem, that's not because it's good for you. It's because it's good for them. That's how they will take you and your data hostage, own you and rip you off.
I'm hoping to see a crowdfunding effort for an ever-growing integrated suite of modular home automation & assistance devices and software (preferably FOSS; you pay just for the devices, which will be interoperable and obtainable from multiple rival sources) which you can buy once and never pay another penny for, until and unless you want to upgrade the hardware. In fact, why isn't someone doing it already? Are they?