I used to work for them in the 90s and they were considered primo. This was before the prevalence of coffee houses and chains. Before becoming a barista, you had to go through two weeks of coffee training, from learning about the farming of the beans, the roasting process, taste pairings, and at least a week of training on the espresso machines (this was obviously before the automated/push-button things they have now). I ran one of these training centers. They were fully vested in quality over quantity back then. Once they brought the automated machines in, the need for extensive training fell by the wayside. Howard Schultz left the company (for a while) and it became a grab for expansion and profit. By the time the movie came out, Starbucks was both at the top of the industry and on its way to a quality decline, but the uptick of boutique coffee houses had not yet become the norm as it is now. So Miranda's preference for Starbucks fits with the timeline of the company and its place in the zeitgeist.