Does anyone think, as I tend to think, that the reason larger capital investments are fewer at SDC than a DW is that they don't need to make such large investments? I mean, many of us come to the park because of nostalgia, because we want our children to experience it the way we did, because it's a local icon that we can't escape, because it's atmosphere is wholesome. Sure, a few come because of the biggest and latest feature that has been added, but as long as they get their "fix" every few years, they'll come back. Now, as for Dollywood, perhaps the same cannot be said: the "base" crowd is not as established and loyal, so the "base" crowd becomes the people they can lure with Dolly's publicity, the latest park award, and the glitz and flash of high-thrill rides.
I'm just guessing TPTB know something we don't about crowds and appeal. I don't always like their decisions, but they may be onto something by spreading the thrills over longer periods at SDC while making costly, but necessary, investments at DW and other places.