I have not been interested in clans in a long time. Clans nowadays are a whirlwind of hashtags, egos and attitude. Honor Pking died a long time ago and the stigma about the big dog clans DDOSing, hacking, cheating, crashing and disrespectful conduct are alive and well.
There is also an imbalance of clans, there is only a handful of relevant clans nowadays, and one clan always in the spotlight for good and bad reasons. There used to be more with some of the older now dead clans sounding like they were polite and just wanted to have fun while still being competitive, not to say people don't have fun in clans anymore, but the clan community is at war with itself too much and the whole thing seems to be taken far more seriously than it used to be.
The financial costs of clanning is something to consider as well. You have to fund your own losses in clan wars, and you will die, a lot. It's the best and worst parts of RS's death system at work, Other games PVP just has you respawn somewhere for another go until an objective, but RS is unique and interesting, you spill almost everything you have on you when you die and if skulled everything your prayer can't save. It's not something I would ever suggest changing, it's a massive part of the charm but having to fund your own way is rough.
Lastly there is a time element, Not only are clans maxed, or perfectly built pures. You also have to attend every event to be a productive member of the clan. The community ages, some work, some even have a family and other commitments now. Runescape is one of the longest grinds in modern video-games, it is it's greatest strength and weakness.
For clans to get better, I think it starts with the community, there needs to be a better community devoid of the politics, the drama. and just be a bunch of friends goofing off having a good time in a video game they love. People want that out of clans, and they get it in communities now whether they PK or not. And yes there are plenty of smaller clans that I am sure do that, but the big boys are playing to win now.