How I see it, is that the problem for new generation of players is simply the huge, impossible gap from start to the top. The game has been around for so long, that a new player with no knowledge of the game has pretty much no chances to keep up with the players who have played longer, trained their skills and made their wealth already. Let's face it, huge part of RuneScapes competetive and efficient gameplay is result of hiscores, skillcapes and show off items like rares. Reaching higher end of hiscores is not even possible anymore, as all the highest ranks already have maxed 200m experience, and for new player starting the skill going for 200m experience seems total madness. It will take multiple years to reach even 99s, unless you're really dedicated and fast to learn.
The players with already higher levels keep gaining more and more wealth while newer players try to accumulate enough for some mediocre gear and items, while the best gear and most rare items keep going further away from new players grasp. Of course, this doesn't rule out all the players, and I'm not saying someone starting now couldn't someday be a "famous endgame player", but it really rules 99% of other new players out from it. It doesn't either mean that it would stop all new players from starting, but it will definitely stop some.
I think we just need more and more content, variation and as said before - better graphics, more interesting quests, more choices and more activities - to give players the more feel of achievement while playing. Instead of having to compete against players who have already played 5-10 years and already maxed everything.
I'm not sure that new players are even aware of that problem with the hiscores, nor would it matter to them much until they actually got hooked to the game and actually want to compete (lol the only competition in runescape is who can no life the most...).
Getting 99's is also getting easier and easier all the time, so that's encouraging for the newbies.