The Soviet Mikoyan-Gurevich MiG-25 was manufactured principally from stainless steel.

The result was a stunningly fast fighter aircraft, capable of Mach 3.2, though in practice engine overheating restricted operation maximum to Mach 2.83 (3,000 km/h), and even that for only 5 minutes at a time as the airframe and fuel would overheat. The MiG-25's mass necessitated huge wings (and overall dimensions), and limited maneuverability. Steel however provided better thermal-tolerance capabilities than aluminium, and lower cost and easier fabrication than titanium.

First flight 1964, introduced to active service in 1970.

That said, the aircraft is notable as an exception to your generally-applicable rule.

<https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-25>

I suspect carbon fibre would also have thermal limitations for high-speed aircraft.

This aircraft also sparked development of the F15 which was superior to anything soviet for 10+ years

Sure but the f15 didn’t start production until almost a decade later.