I see we have ourselves a defensive Chiefs fan.
As you said yourself, Gonzo is a TE. A great one (albeit starting to show his age now), but a TE nonetheless and not a WR. Hence my comment. When your team's two most dangerous receiving threats are a TE and RB, respectively, jokes about the anonymity of its receiving corps are to be expected.
In 2006, KC QBs combined for just over 3200 passing yards. Of that, Gonzo and LJ combined for 114 catches for 1,310 yards, and the top 3 WRs on the roster
combined caught 120 balls for 1,625 yards. Those are Charger-esque stats, another team for which the "_____ has WRs?" joke is applicable.
The fact is that the Chiefs haven't had an elite WR threat in, well, forever. Kennison put up some decent numbers over the past few years, but I would argue that was mainly due to the attention that Gonzo and Priest/LJ drew. He certainly doesn't strike fear into any defensive coordinator's heart, and teams certainly don't have to game plan against him.
To reinforce my point: quick, name the best WR in Chiefs history!
<crickets chirping>