There is something unique about projected slides onto a good screen. The shadow details combined with just the size of the image can be quite impressive.
Kodakchrome produced great color images, but the chemistry to process it was fairly complex as well as toxic.
When next day processing was really taking off (the 80s?) Kodachrome was AFAIR the only media that had to be sent off to Kodak for processing. Complexity and toxicity explains that. Its wiki page is a sort of black hole to lose time in.
https://en.wikipedia.org/wiki/Kodachrome
Later Ektachromes were pretty good. By the time Kodachrome went away, there wasn't really a Kodachrome 25 replacement but the 100 ISO Ektachromes were very high quality.