Smartthings never did manufacture those sensors, they were created by third parties and then branded “smartthings.“
Those models are now being taken over by Aeotec, in many cases still manufactured by the same third parties, just now Branded Aeotec. They are expected to be on the market in a few months. So if you like those and you’re willing to wait, you should be able to get them again
And here’s the official announcement from smartthings:
An Update Regarding our Hardware
I’ll leave it to others to discuss other options.
I will say that historically zigbee has been better than Z wave at power usage, which is why zigbee battery powered sensors tend to offer shorter reporting times, because they can still make their batteries last.