To everyone looking back nostalgically to River Country I think you are looking through very thick Rose Colored Glasses.
Disclaimer: This review is from someone who first visited RC as a teenager and then as a father with a 6 and 7 year old.
River Country was a first gen water park. Not at all like water parks today. Today RC would be an insurance nightmare.
The water for all the slides came from the lake. They supposedly treated it, but it was greenish brown.
Some of the body slides (not just the "shotgun" slides at the pool) dumped you into over 6 feet of water. Everyone had to be a strong swimmer but at the time there were no "height" limits. In order for younger ones to use the slides you had to go down first, tread water and then push them to the ropes that defined the splash down area.
If you went under and stayed under, good luck, the water viability was maybe 2 feet if that. The life guards would have had to search for you or your kids blindly.
The real pool had rocks around it for diving, yes diving, at one time in this country diving was encouraged.
So besides that, other issues that it was much smaller than the other water parks and it was tough to get to* I can see why it closed.
* At the time RC was built it was in the middle of what was WDW. As they started to build other parks and resorts it was now in a lost corner of the world. If you told guests that at one time there was a water park near the campground in WDW they would ask "There's a campground in WDW?

"
Sorry to burst everyone's bubble.
Oh and yes I too have a very special place in my heart for RC.