Haven't flown through CLT in a while. I was wondering if the lines are still very long?

That would depend on time of day, how many flights are in, day or time of the year and many other out of control factors.

And staffing levels, which seems to be a major problem. IF there are multiple international flights arriving within the same time slot, passengers are often kept on the plane due to the immigration area being totally full.

Coming from SXM in mid-December, on a Friday, we were through in less than five minutes. Baggage was another story, but we still made our connection in plenty of time. We do have Global Entry, which sped things up, but they have kiosks for all passengers now, so the process is faster than it was a few years ago, even if you don't have GE.