Of course it is "easy" to do - but perhaps UNESCO deserves it also!!
A couple of quotes from a blog article from earlier this year titled "UNESCO Desk Jockeys and the Archaeological Heritage" bemoaning how little of UNESCO's action is focussed on the protection of Archaeological sites. The author may be unfair but appears to have some knowledge of the area. And his criticism can't really be related back to UNESCO's lack of money - what he is complaining about is a mind-set
"My experience is that UNESCO refused to help save a site in Syria, and that they are better desk-jockeys, writing reports rather than actually getting off their arses to do something to help"
and
"UNESCO is indeed, as Dr King is not alone in thinking, basically focussed largely on an elite group of getting together, talking glibly about how they are creating 'world peace' and 'dialogue', issuing lofty Recommendations, making a seemingly interminable number of "Lists" (to what aim is less clear), heaping honours on their pals ('Collector Named UNESCO Goodwill Ambassador') etc etc. In the end, however, one has to ask what the actual effects of all this talk, all those meetings, all these "lists" actually are on the ground"

See http://paul-barford.blogspot.co.uk/2013/02/unesco-desk-jockeys-and-archaeological.htm l

The points made in that blog article are understandable. However, UNESCO (like the other UN entities) is a political grouping of various member states, and does not really have the power / the will to rock the boat - and ultimately to change anything. Contrary to other international bodies (such as the WTO or the UN Security Council - when the latter is in agreement) it cannot issue sanctions apart from deleting a site from the WH List (which has no consequence for a member state except in terms of reputation, and does nothing to help the site in question). Furthermore, due to its antics in other areas, it has no budget to actually really help maintain any of the sites on the WH List. Instead, it has over the years refined an ever more complex list management bureaucracy - even for the flagship World Heritage list - which has vastly increased the burden of nominating a new site, especially for poor countries (consider e.g. Madagascar this year, comparing to the millions the Chinese apparently spend on each nomination). Its periodic review can help raise awareness for deteriorating sites or planned constructions that would have a negative impact on the site (St Petersburg comes to mind), but it leaves the real assistance to NGOs or to member states.

Is it UNESCO's fault? Under different management, it could have been more assertive and more impact-driven. But given the political games in the background, maybe we all just expect too much of it.