Everyone has an agenda. I wouldn't criticise you for remaining cautious/suspicious but I would criticise you if you automatically sided with the narrative of the US/UK/NATO governments (or mainstream media) because you'd be using flawed logic without having enough of the context and information at hand. That may seem a rather vague comment, but in determining your support or criticism of an organisation it comes down to percentage of trust and I can understand why most would hold a high percentage of trust in their government and in turn, be liable to criticising those that government representatives criticise.
WikiLeaks is a journalistic organisation, founded by an Australian, whose contributing "workforce" is comprised of various nationalities, therefore the organisation itself has no allegiance. Their aim is simply to expose corruption and things they feel is in the public's interest, to the public - the public that diplomatic government is meant to represent. They have no intention of publishing matters of national security (putting populations at risk), for example documents on military capabilities and do not work with any governments. There are inevitably grey areas where governments may have programmes they deem to be of national security but to which WikiLeaks deem public interest. Like how US government is meant to be a system of checks and balances of power in congress, the presidency and judicial systems (a complete failure in my view as it does not account for vested interests such as campaign funding from corporations and has clearly been abused/ignored as proven), you can think of WikiLeaks as factoring the public into the equation in that checks and balances system. Their agenda can be summarised as protecting internet and technology freedoms such as privacy, which has many implications if not protected, regarding things such as right to free-speech.
WikiLeaks helped Edward Snowden, whose revelations I'm sure will prove a very important part in the history of mankind (unless he's wiped from the record at some point), escape the clutches of American intelligence services, gain temporary asylum whilst also getting him legal support; if they hadn't he very well could have been assassinated if US intelligence had the opportunity to stop the leaked info at a single source, or caught whereby he has been unfairly (but legally) charged with the old espionage act despite not being a spy for another nation (I don't believe the act accounts for whistleblowers). In similar cases in the past, whistleblowers did not receive a fair trial in the U.S. which is why he has sought asylum.
If you want to see an example of the kind of work WikiLeaks does and facilitates and why it is so extremely important to people such as yourself (whether you know it or not) and the implications I allude to above, I am about to post another Off-topic thread soon that will be of interest.