True, but with those access times you can wait a lot longer for content to be loaded into RAM. Hard drives are the reason for many years games needed to duplicate their assets, for example, because seek times slowed down loading time and putting the same content in the file twice but at the right place would speed up the loading process significantly. Games today still have special HDD code because of the difference in performance class.

SSDs won't replace RAM but many RAM caches aren't performance critical; sometimes you need your code to be reasonably fast on a laptop with a 5400 rpm hard drive and then you have very little choice of data structures. With the random access patterns SSDs allow this complication quickly disappears. You won't find many Android apps that will cache 8MB block reads to compensate for a spinning hard drive, for example.