This, along with stuff like Inbetweeners, Black Books, Friday Night Dinner etc, is an example of where Brits go a little overboard in rating their humor too highly. Plus, Americans hear a British accent and think it must "British humor". There's nothing British about the humor in this show. It's standard, straightforward universal sitcom humor.
None of these shows are doing anything challenging or inventive. It's safe predictable joke after safe predictable joke. You can see the formula like a baseball pitcher winding up his pitch. And the punchline comes right when and where you'd expect it to land.
If you're interested in seeing some decent British comedy, check out Detectorists, Camping, Mister Winner, Mandy, This Country, Yonderland or even Plebs. There's nothing going on in The IT Crowd that you haven't seen 100 times before.