There's a bit in Sivetz's
Coffee Technology where he claims instant is horrible not because it is instant, but because it is based on such an overextracted brew (in current instant, the coffee is brewed for several days and has a solids extraction of around 50%. The book is out of date, now the coffee is brewed only a few hours, but at 20 bar or so, and the solids extraction is up to 65%

). He said if the instant is made from properly brewed coffee, it tastes acceptable (although still with no dry fragrance, and little wet aroma -- the aroma is typically added by spraying volatile coffee oils into the container).
In other words, commercial instant coffee is not just instant, but also dishonest. Who knows, Starbucks may be making it from an honest brew. That would be a big improvement.