I've seen it time and time again. Someone applies to a guild, gets accepted late in the week, everyone is away for the weekend, or leveling alts, or doing stuff with their families, therefore the many "Anyone need a random?" 's go unanswered, and the new guildy leaves in search of "greener" pastures.
Or someone gets accepted to our guild, coming in as a raid trial, and doesn't get to raid the first week or two due to raid comp and numerous sign ups. And takes it personal. And leaves.
Does this happen in your guild? Have you done this?
Maybe the problem isn't the guild you joined. Maybe it's your way of thinking. If you have the mentality of "what will this guild do for me?" then you are setting yourself up for disappointment. Because frankly, guilds as a general rule don't care how "leet" you say you are, whether or not you need gear (other than whether or not your gear is raid ready), how many hours you spent in MC back in the day therefore "earning" you a spot today, and they don't care how long you've played. They care that you know the current fights, know your class, know not to stand in fire, and can be autonomous--take care of yourself, bringing your own flasks, food, and repair gold. In other words, most guilds don't care to think about what they can do for you. Most guilds want to know what you can do for THEM.
What do you bring to the table? Anything besides leet dps or heals? Will you help members out as they need help--perhaps go do Ring of Blood for lower levels, or learn special patterns as people need them for whatever professions you may have? Will you be willing to--WHOA!--step out for a boss because raid comp needs more ranged? Or more melee? And then jump back in for the next boss, even though you now are short the valor points and the loot the last boss provided? Are you willing to be there for the GUILD?
Not that you have to drop whatever you're doing every time someone in the guild needs help. It shouldn't be a one-man-show all the time--you jumping in to help and no one else helping ever. In fact, if you notice this happening, maybe you should talk to an officer about their policies--it may be that they have a policy of NOT helping alts level, and discourage begging for runs in guild chat.
Good guilds do care for their members. And they will recognize the efforts of those especially that are there for the guild, not just for personal gain or loot.
So, ask not what your guild can do for you. Ask what you can do for your guild.
And if you are still getting ignored after doing this, then maybe you are in the wrong guild after all.