Midway campground in Big Cypress Preserve

Did you have the right address or Lat and Long digits?
Your right the dark of night and rain make travel difficult. That is why we always plan to be off the road long before sundown.
Eleven years fulltime and only once have we pulled in after sundown.

While I think we all get your point. Trying to find any CG in a remote area in the dark and rain can be difficult.
BTDT it's best to avoid night travel. As much as I try to avoid night travel, I do occaisionally find myself traveling at night.
One rule I have made for myself is to not arrive at a unfamiliar CG in the dark. If I'm familair with the place, I can get by in the dark. But if I am unfamiliar,I will not arrive in the dark.
Avoiding a night time arrival sometimes means delaying my departure until morning.
Note to self: Always plan trips to unfamilar places such that your arrival is during daylight hours.

This was about the destination as most of my travels while working are. The address they sent me was to the welcome center, not the campground.

I've made that mistake too. I won't call it a rookie error, but in time you learn to be sure the address you have is for the CG.
This is particularly true for public parks that may have a lot of areas and a lot of entrances other than the CG.
Going to the wrong address in the dark and rain is the triple whammy!

I don't know how far you went past the welcome center looking for Midway, but it's not hard to spot as the sign is on the side of US-41 and the campground is just a hundred feet or so off the road.

Why didn't you overnight in the welcome center?

If you saw the sign for Midway, you were there.... there is only 1 sign and it's right at the entrance road as shown in the post above. Since you were at Midway, how could you travel 2 hours without finding a place ? It's 45 minutes to either Miami or Naples?

Anyway, I try to always get to my destination prior to dark.... sometimes issues prevent that. At least you found a place to rest... frustrating, been there /done that