Just to add on that.

In 2015, Paris Airport Air Traffic Software were running on windows 3.1.

Is windows 3.1 outdated ? Yes. No longer a public facing product ? Yes.

Dead ? Absolutely not (at least back then, maybe it got decommissioned).

Around that time, a friend of mine was doing his master Thesis in an astronomy lab. He had to load fortran 77 routines from a 5" floppy disk that were doing critical computation (they were in the process of migrating). Same diagnosis: outdated, became a niche product, but not dead at all.