Different people have different priorities.
I’m quadriparetic (use a wheelchair and have limited hand function). Voice control is essential to me in considering any system.
Before echo was available in the US, I used IFTTT with Siri for voice control of smartthings, as detailed in the voice command solution thread in the forum. It’s much clunkier than echo, but it works. There are other voice command options, but I think all of them require oauth to access a third-party service.
I had already discussed the IFTTT option with some people in one of my online wheelchair groups who are in the UK. It definitely would be a significant factor in their choice of a SmartThings purchase.
As the old saying goes, “your use case is not my use case.” 
Something that seems trivial to one person may be essential to someone else. One of the strengths of SmartThings is its openness and the fact that different people do use it differently. I, too, am surprised that the system launched with the OAuth problem. But it did, and they’re working on it, so it’s up to each individual person whether they want to return the system and try again later, or move on to something else, or use the other features for now. There isn’t going to be any one right answer, it just depends on each individual’s particular needs.
- for those interested in voice command options other than echo, see the following topic. This is a clickable link. Again, though, I think all these options will require that the oauth issue be fixed before you can use them.