I think that Darkness meant, that since 1.07 they have become less useful.
The major benefits (prior) were the guild tasks (keys/gems/maps) and mastery benefits (mana surge).
In 1.07, kingdom leveling changed from Souls (by leveling up all troops) to Gold (paying for each level increase). This was exacerbated by the need for traitstones & duplicate troops (for ascension) in 1.08. These changes have generally resulted in less donations to guild tasks than in the past.
If this lever can be adjusted somehow to rejuvenate the importance of donating to guild tasks, then the guilds would again become very useful.
If you wanna be in a good guild it means you also have to play the game regulary, mac. Without playing much you doesnt really have something to give to the guild and you will get fired from it. I am not talking of myself, I am in a guild and I play regulary.