With the release of the Notice 4 revision to the standard on July 31, 1996, MIL-STD-1750A was declared inactive for new military projects in the USA. However, both the Indian Space Research Organisation (ISRO) and the Chinese aerospace industry continue to use the 1750 for new projects.
To necessarily say the CPU is technologically defunct can be nebulous. This CPU can run at 0.5 MIPS to 3 MIPS depending on the operating speed (from 1 MHz to 20 MHz). The lack of modern floating point capabilities makes this CPU less suitable for some (but not all) modern embedded applications. However, lack of familiarity (and modern compiler support) with this CPU makes its uptake in the civilian computing sector difficult.
More modern CPUs like the Mongoose-V (used on the New Horizons spacecraft), the higher performance RAD750, and the freely-licensable SPARC-based LEON are replacing the MIL-STD-1750A in the space sector over time.