Is it possible there are a good handful of serial killers who will never know about? From the 60s-early 90s

The late 1960s to around the early 1990s I think can reasonably called the golden age of the serial killer.

No DNA. Lots of random crime in general obscuring theirs. Tons of murders in general. Cities with budget issues. Police departments not communicating well, a less organised FBI compared to today, no CCTV cameras, DNA either being unknown as a LE tool (60s-70s) or being in it’s very infancy (80s-early 90s)

We know of several dozen serial killers just in NA alone in this era. We even know “unknown” killers like Zodiac because he took credit for his crimes in a very public way.

Is it possible however that we have serial killers from this era who we don’t even know, in terms of their crimes being connected to even one unknown individual?

Consider that with Zodiac, a big reason we connect those crimes to an individual identity, is because the suspect not only claimed credit but also gave pretty sound evidence to the police of his involvement.

If Zodiac hadn’t sought attention, would his crimes have ever been connected?

Likewise, do you think there are a handful or more killers from this era who built up a body count, but whose murders have gone unconnected specifically because they didn’t publicise themselves, and either had the self control or luck to not get caught?