Problem: Reliance on the Random Number Generator for drops.
Solution: Activities like FATEs, dungeons, raids, and select (soloable) quests should yield currency toward gear and crafting materials specific to their level range with an option convert them higher or lower at varied ratios. Ultimately, this is to prevent situations where someone might go 0/20+ on a single item. You can still have the item drop via RNG, but people should always have an alternative path to something. As an added option, if undesired items do drop, the player/party can decide to "destroy" it and instead be rewarded with extra points.
As for making participation in a guild/linkshell/whatever mean more, I've seen a few games try to implement points for activities you otherwise do and can spend toward the guild. Sometimes it's for (temporary) buffs, occasionally it'll unlock features like a guild vault, and something I like is offering alternative sources for things like rare craft materials. There's a browser game out there called Wartune (A bit too P2W for most tastes, I'd wager), but its guild system basically ran on contribution generated by players. You had the quest/event stuff, but periodically you'd get invaders that attack your "home base" so to speak to give players a means to generate more contribution. If you have an excess of gold, you could also pay it toward the guild. In turn, the guild could buy more buildings, upgrade them and their functions, and unlock buffs. Everyone's contribution is viewable within the roster, so you can see who's been doing things for the guild and not as long as their total count keeps climbing. A feature to promote a little extra contribution involves a prize wheel. Most of the time you probably get junk, but occasionally you'll get rare/good things.
While I wouldn't say to do it the exact same way, it's a good means to allow people who can't consistently raid to still be useful to a group in their own ways, particularly if paired with the concepts Kashius mentioned earlier. One problem with Wartune, however, is I've noticed people get spread thin over guilds hoping theirs will be "the best" and, in turn, you get a bunch of weak guilds instead of a couple strong ones. Those who play more will want to leave these weaker guilds for the better ones with better buffs, while everyone else keeps trying to poach members from others to improve their ranks. Should it come to a point where a guild folds, there is means for another to "absorb" its resources and basically prevent the effort of others from becoming a waste. As such, if there is some element of contribution system implemented, a means to adopt these lesser guilds into a bigger one should be present. Perhaps it shouldn't be a 1:1 resource gain to prevent people from starting multiple guilds to potentially power up x times faster than intended, but you could also put some kind of time limit to these acquisitions, perhaps longer based on the strength of the lesser guild being taken in.