Since the release of Old School RuneScape (OSRS) in 2013, RuneScape 3 (RS3), the original game that has been updated through the modern era, has been on a downward trend, having now lost over 57% of its player base, with an average of 46,403 concurrent players in 2013 down to an average of just 18,3
Props to that site and article for actually being readable on mobile.