Ramjets do live on to an extent, in NASA technological demonstrators but also more interestingly in the SR-71's legendary J58 engines, which switch to from mostly turbojet at low speeds to mostly ramjet at high speeds: the compressor is almost entirely bypassed then[0] and the vast majority of thrust comes from the "afterburner", hence the engine's maximum efficiency being around Mach 3.2.
[0] https://en.wikipedia.org/wiki/Pratt_%26_Whitney_J58#/media/F...