Kingdom's a really great guild if you're hardcore.
If you're casual it's still good ... just less good. There's the aforementioned dues, as well as the (expensive) item requirements, but all high-end guilds have those to some extent, not just Kingdom. There's also the fact that you have to pay hundreds of DKP for a Sleeper's key when all the hardcore people got them loot council-ed for free (sadly that's a uniquely Kingdom thing
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But none of that is insurmountable, and it's still a guild (the only?) where you can see top-end raids and get top-end loot as a casual ... you just have to accept that the guild is run by/for the hardcore people.