See the thing is, in 2001-2006 this game was very popular. Another thing that wasn't as popular is the E-sports and gaming industry in general. With the E-sports gaming industry, the Youtube industry, Twitch industry, and the whole online gaming community growing the way it has - we have been left with a game which will be on a gradual slow decline.
It's not like back in the day where 1Billion gold was enough for all of the best Barrow's armour, Dragon, etc. In this day and age, players have learned much about professional and efficient gaming that there is virtually nobody playing RuneScape without the use of Youtube, guides, blackmarkets, etc.
The gaming world has changed alot, this game is not going to last forever, and the new players who do join will learn how to max accounts very fast, and with the amount of players who have billions and billions of gold, ambition to continue to play and be one of the best will not be there with anyone because of how efficient people have become and how easily it can be impossible to catch up to someone.
I don't know if this makes sense but it's how I feel.