To be honest, I don’t blame you! Although overall the hub is only a small part of the overall setup in terms of cost, like most cloud based hubs buying into a system with questionable supply isn’t great!
I bought ST with the acceptance that if ST vanishes (although I chose ST based on a friends recommendation and large name behind them), I would probably then look at getting a more expensive hub that is not reliant on the cloud, but could utilise services within it (this is the way Honeywell Evohome works and is one of the reasons why I picked it, where as the rest seem to have a heavy reliance upon the cloud to operate)
Hopefully its just a blip and they will get the issues sorted.
As for “cobble together Z-wave stuff”, that isn’t the case, and to be fair, the devices you buy could be transferred to another zwave based system. Yes, there are branded smart things stuff, but they don’t make things like in-wall relays for example. I have a couple of in-wall relays and use Belkin Wemo bulbs and they work perfectly other than the odd, infrequent hiccup. Even the ST branded stuff has issues (such as door sensors getting stuck in one state). Some kit is better than others, but to really expand on your experience, you need to venture outside of “ST branded” stuff and link it in and get your hands dirty with code (even if its just copy/paste somebody else’s great work)