The article, dismayingly, matches up with my own experience.

I was at the IAEA for 3 years, the first year as an intern and then two more as regular staff, coding tools for weapons inspectors. The organization is hardly irrelevant, so one would expect it to be better than some of the smaller and more obscure organizations like in the article.

In some ways, it was better, but not in many. The IAEA interns were paid, though not by the IAEA itself but by sponsoring countries. I was friends with interns from other organizations who, much as the article reports, were frequently unpaid, idle, disinterested, there for too short a time to do serious work anyway, and mostly interested in networking and partying.

Some further responses:

"The first one is to pay the salaries and the perks of its employees."
Oh yes. I'm surprised the article doesn't mention that the salaries are tax free (international civil servants are tax exempt). They're explicitly tuned to be "average for the position in the given field", but then they're not taxed, so you're automatically making 30-40% above average for your field. Furthermore, regular benefits like health insurance and retirement are extremely generous, and are topped up by all sorts of perks such as rent-assistance, grants for cars, daycare, and higher education, generous allowances for all sorts of things such as paid home leave and subsidized moving. Many of the employees were explicitly there until retirement because they knew of no other place to get such generous treatment with so little demanded in return. Because if you had a permanent contract, then oh yes there was quite little demanded in return, firings were unheard of and a good number of staff spent half the days chatting on the phone or drinking coffee in one of the many cafes.

"Fixed term contracts are the holy grail"
Yes oh yes. Most of the younger people were on short-term contracts, which lasted a year. It was understood that if you pay your dues to the powers that be, your contract would be extended over and over, with a significant pay-bump each time, until you got a permanent one. The machinery of contract extension was inscrutable. You would hear nothing back and typically your contract would be renewed on the day your last one expired. Sometimes they'd blow it by a few days and people would end up sitting around at home waiting to hear if they were really jobless or not. Rock the boat a bit, and that renewal would be much less certain. The ambitious and engaged minority tended to get fed up with this after a few years, leaving only those who desperately desperately wanted the cushy perks-for-life hanging on for those fixed term contracts.

Finally
"rules apply only to the powerless"
Yes oh yes. The whole organization was hidebound and rules-driven, except when miraculously, it wasn't. Over and over, the stonewalling would stop, the doors would open, and the structure would rearrange itself in order to accommodate someone. You never knew why it happened, and it was never discussed.

Overrall, I have to say that the experience was disillusioning, I believed (and still do) in the mission and importance of the IAEA and the non-proliferation treaty. It was hard to accept the degree to which the organization had become the plaything of the entitled and the powerful.