While it's unrealistic to believe that RS3 will ever overtake OSRS in popularity, RS3 has an incredibly special place in my heart. I've been playing since 2008 and I remember a time when players talked and spent time together a lot more outside of the monotonous skill grind or PVM encounters.
Over the last few days, I've tried socializing more on RS3 W2 and I've gotten some pretty mixed results. I met a player who still does drop parties. I chatted with a new player who seemed to really be enjoying the game. But most of my interactions were met with silence. Even my current guild, which has on average 475/500 players can have a great deal of radio silence. This is to be expected, of course. A lot of players AFK and many features in the game enable that. There are also players who struggle with being comfortable in social interactions, even online; and that's completely understandable.
Still, I think one of the reasons RS3 struggles so much in popularity in comparison to OSRS (besides the fact that there is so many features that it can feel overwhelming to even seasoned players) is that there isn't as much of a sense of community as there was in older iterations of the game. I'm sure there are a multitude of things that could be done to fix this, ranging from adding fresh coats of paint to some skills or replacing dead features in-game with new activities, but neither of those are things I, as a player, have control over and depend entirely upon Jagex themselves.
I thought long and hard about what I could do to improve the social climate of RS3 and an idea that really sticks out to me is to create a guild that's main goal is to improve RS3's community through friendly chat and assistance to anyone who needs it. Of course, making a guild requires five players. I would need to find people interested in this goal as well. If anyone would like to see RS3 reach its social potential, feel free to drop a comment on this thread.
Let friendships bloom wherever you leave footprints
I often think about this too, regarding the social aspect. When we had the beach event, that's something you got to see a lot is people talking again whilst they skilled. Not that it's gone entirely, since being F2P based, there's always lots of chatter in W3. There's certainly been a decline in a lot of the "social skilling" that used to take place years and years ago, and this has been (in my opinion at least!) because of a couple things:
1. The increase in super afk-able skilling methods that still result in tons of exp/hour which also incentivizes "altscape" (thus, less people paying attention to the one screen at a time, which admittedly I am guilty of too!)
2. The myriads of different chats that people can use now, including discords. There's friend chats, clan chats, group chats, discord chats, and who knows what else I might be forgetting.
This has lead to more of a clan or niche group focus for many things instead of in the broad community sense.
Anyways, that's just my opinion but I digress;
If I may give an idea to help with your pursuit of this (I hope that's alright); Consider getting involved with hosting broad/general community events such as hide 'n' seek, skill & chills, minigames that everyone can participate in (possibly think about aligning it with the spotlight minigame for thaler point rewards). In my opinion, events are one of the best things to bring communities together. Not just from one clan hosting events- but rather events for multiple clans to come together.
I like this goal, though & I wish you the best with your endeavors!