The content wasn't outdated, it was mostly a look into the imagined future most of which still hasn't happened. How do we define outdated. To me it is stuff that has already happened being depicted as the future. In that sense it was not outdated just not repetitive. After the first few times it just wasn't exciting to look at. That is in direct conflict with PoC and HM which are fun but mostly nostalgic. Horizons was a good ride in it's time had a different ride vehicle but was disappointing in many area, especially the ending. Even though the concept of choosing you own scene was creative and the technology was outstanding the finished product was blurry, sometime unidentifiable, lacking in clear quality and a disappointment to me. Great idea, poor outcome. That part was the part that needed upgrading. Pirates and HM are timeless because they tell a non-reality story that only needs to be dusted off on occasion. There is not expectations or even idea that it is outdated. How could it be, they are there strictly for entertainment and does not attempt to predict anything. That is what makes them timeless.
The major part is our inability to understand that those that still think it was a mistake to get rid of it are a minority. That group were not enough to pay the bills so to speak. Mission: Space was exciting and let you semi experience the real thing. It had the misfortune of two people dyeing while on the ride, early on. Either a case of unknown medical problems or failure to take the massive warnings posted everywhere seriously. That set it back and gave it a bad reputation. It was much shorter then Horizons, but it really did pack a lot of excitement and imagined participation and control in that short time. It is the only ride that, when over, I loudly exclaimed "that was awesome". I have mostly always enjoyed all the rides at WDW, but never to that extent. I strongly do not appreciate the alteration to the Green side. It isn't at all the same experience and is proof that "updating" especially with Disney, is not often an improvement. I always loved the Orange Side, health changes make riding it close to a Kamikaze mission for me. So I do heed the warning signs now to avoid being a statistic.