Technological development is driven by sales - these big electronics companies can only drive the market sector forward if people buy the products.
There are undoubtedly some pretty complex technical challenges to be overcome when developing smartphones, and the sector is unbelievably competitive. This may tempt manufacturers to rush products to market before they have been thoroughly tested by consumers in everyday situations.
I'm not saying that this was the case with the Samsung S8 - I have no way of knowing. It's possible that the reboot problem might be resolved with a software patch, and I imagine a lot of hard work is going into that right now.
I certainly don't see this issue as indicative that "the technology today is the pinnacle of the tech available within the battery power available."