Sure, but if it wasn't for vulture capitalism trying to cut every cent possible, it'd be a minor increase in cost to make these systems degrade gracefully. Then at worst it'd still function as the equivalent 'dumb' device.

Yes and no.

More complex systems can be engineered to be quite reliable. But there is little incentive to not make that sensor in the bulb as cheap as possible.

There are commercial solutions that are overkill, like bacnet. Which work more like industrial automation than fancy apps on your phone. Extra wires are run all over the facilitate communication between devices and work more with analog inputs and outputs. Having strong relays on circuits is far more reliable than a few relays inside bulbs where they get hottest and subject to the biggest thermal swings.

Smart homes run as consumer setups are a fucking mismatch of half finished environments where nothing is truly integrating everything. They are slowly built as new devices are made "smart." And even going prosumer it's still a hodgepodge solution.

Then there is the lack of vision. When people say "smart home" they have some mental image of the house doing all this cool stuff on its own. But only those who actually play with it will set some of those automations up. And in my personal experience, there isn't all that much "smart" that needs to be done in a home. If the home owners aren't thinking what the outcome is or what automations they will use, then it's just a bunch of IoT shit sitting there mostly unused.