Its pretty much impossible to bring people into main clanning if they aren't already familiar with the way clans work because there's no incentives beyond the action itself. You get recruited by a clan and they immediately want you to drop mills on gear without even experiencing an event, and then during the event you're expected to lose that gear without looting anything back from the people you kill. Not all clans started out like this, there was a food chain with lower tier clans that would take advantage of the big Sunday rune wars to go get looty and have fun whilst the top clans distinguished themselves by having a 0 tolerance policy on looting and demanding a higher standard from their members.
The fact is there is no place for the lower tier clans in the current food chain, the player base has massively shifted away from PVP and the established clans and teams are far too good to try and come in dry with completely fresh faces.
With that said as the people already involved in the scene our priority should be to keep things as clean as possible, from what I understand WL dropped their crash war and thats a great step forward; I know I wouldn't want my clan to fight WL if it meant we'd be having some stupid 1v2 with whoever they're beefing with; if I beat Wilderland I want it to be Zerg Unit that beats Wilderland not Zerg Unit and 20 other dudes who are obligated to come harrass WL and vice versa. Like how am I supposed to get my guys hyped up about winning a 2v1? Especially when we're neutral as fuck and don't have a clue why you're beefing or who you're beefing with.
Something I'd like to see is less multi clanning/teaming. I know its been like this for years in the interest of action but as a pure I value having 1 team or clan I can get behind. My first adventure into top level main clanning was with the team Martians and I was proud as heck to be a Martian, thats my team, thats who I ride for but if the team we're fighting under-pulled or didn't have a caller we'd just send them some of our guys. At that point it feels less like a fight that matters and more like inners or a fuck around game with your buddies. I came to take the other teams head off and instead its just a bunch of my pals over there making fun of each other for getting 1 hit.
rambled on a bit just some thoughts
EDIT: Also as someone else pointed out they need to do something about return methods in the wilderness; everything from burning amulets to ancient tabs to games necklaces these things have been a MASSIVE detriment to both pure and main clanning.