Counterpoint: single threaded performance hasn't improved much in the past 20 years. Maybe 5x at best. And virtually every UI programming environment still has problems with work done on the main thread.
RAM parallel bandwidth, increased caching levels and size, and better caching rules, instruction re-ordering, predictive branching, register optimization, vector instructions, ... there have been many advances in single thread execution since the 90's. Beyond any clock speed advances.
