Design makes all the difference and creates real business (and user experience) value.
Is it? With everyone talking about it here how important it is, I get the feeling it is over hyped. There is also not a lot or maybe actually no proof at all these sites became popular because of design. They threw massive amounts of VC money into marketing and networking and ads etc. And next to that they went viral (probably because of the massive amounts of vc money and people in influencer circles egging eachother on, for which you can find traces on HN and reddit easily): would be great to see some actual references how you came to say with such certainty this is 'because of design'.
For many, design also refers to how a product solves a people problem, how does it affect people’s lives, what’s it worth ...
People who practice (product) design spend time looking at usage data, talking to people and understanding what the impact of a design change is.
I think most will agree those are essential things for a product to be successful.
But it does also apply to your definition somewhat though: if we were marketing forcefed a solution which made (possibly better designed per your definition) competitors die, is this excellent design (per your definition) or is everyone parotting eachother because they had enough cash to 'win the race' and are therefor the new standard? Which has nothing to do with design (even in your broader definition).
Ps. I do agree with you but very much feel that GP is mostly talking about graphical design, which I simply do not think is as important as designers think it is. Compared to most other aspects.
Yes, design adds value, but the graphical aspect (margins, branding, etc) adds less than you think. In my view, given two technically equal systems, design only decides which system users will gravitate towards. Without good design, users will happily use your system, unless they know that there is a better-looking version of the same system elsewhere.
So this makes graphical design mandatory, but in a way that is to a great extent decoupled from value.