Inspiration Tower and the Zipline were both good attempts at diversification, but the implementation of both was somewhat lacking and they never kept truly trying to improve. The tower felt dated last time I was there, but it could still be an amazing attraction with some fairly simple renovations. The zipline was amazing, but it was expensive, and once you were done there wasn't much to do. The tower and zipline were kind of separated from the rest of the SOTH, which never really made sense. They should have stopped doing the tram tour long ago and let people walk between the tower, cabin, and the rest of the complex.
I wish we could go back in time and convince them to refocus on things like festivals with food trucks and bluegrass. Adding in an RV/camping/cabin resort would have been easy as well. Then you add in more attractions such as an alpine slide.
They never really understood how to properly diversify or reinvest in their other attractions. They assumed the show was all that mattered in the end. You simply can't get complacent when running a business, even when things are going well. As much as we complain about how things change at SDC, the park wouldn't have kept going these days if it was just a cave with some crafts and shops around it.