I've used a lot of systems/libraries/etc. which claim to be "simple", but are really anything but. In many cases, "simple" equals to "primitive", which means that as soon as I move beyond the five-line example from the README I'm very likely to stumble upon a problem which will easily take a couple of days of furious googling, code-reading and issue-creating to get around.

I don't think it's insulting my competence, it's just that "simple" is a sign that the original developer is not aware of the complexity (SNMP, anyone?) and hence it's now a trigger word for "prepare to be miserable for a while". And I don't like to feel miserable while dissecting something someone called "simple".