Operation Dumbo Drop had nothing whatsoever to do with the original Dumbo, other than they both featured an elephant. Oh, and they used "When I See an Elephant Fly" at the end. That's it, really.
The 1994 Jungle Book was hardly a remake either, since it took the story in a completely different direction. The plot had more in common with 1999's Tarzan than it did with Disney's 1967 animated version.
I would argue that the first real "live action remake" that kept relatively close to the plot and spirit of the original was 101 Dalmations from 1996, but this was somewhat of a one-off. The trend really didn't start until the 2010s, with Alice in Wonderland and Cinderella.