Sounds about right...what were your RPM's in 5th gear?
5th gear is not designed as an accelerating gear...it's designed to lower your engine's RPMs at highway speeds in order to use less gas. Basically, once you're up to the speed you want to be at, you shift into 5th. Although you should have the ability to accelerate slowly, but it ain't gonna pull hard. The 33's might be the cause of you not being able to accelerate at all though. If that's the case, you'll want to look into regearing your Jeep for that size of tires.