No Stupid Questions

There's estimated to be upwards of 50 serial killers currently active in the US today.

It is much harder to be a serial killer now, but police are still not great at their jobs and especially communicating across state lines. Hell, even communicating across county lines have proven to be too difficult for police to manage or care to do. This is one of the reasons serial killers target sex workers, queer people, and people of color the most - the broader public care less about these victims and the police don't work as hard to solve their murders.

Theory:

Healthcare CEOs seem to be doing well.

Motiveless murder/disappearance - that is, where the victim has no enemies or any reason to have become a victim of murder (e.g. robbery) - are extremely hard to solve even today. Police are much better able to capture criminals today, but they're still batting a pretty measly average overall, and especially so in cases of motiveless disappearances. The US has ~350 million people in it, and there are enormous swathes of land that are uninhabited or are only lightly inhabited. Massive marshes, endless forests, etc. Dumping bodies in there is so effective that sometimes even serial killers who have confessed and are helping the cops locate victims' bodies can't find them all.

The behaviour of killers outside of the crime itself is usually what fucks them. Bragging to people, taunting the cops, leaving calling cards/clues, or just becoming so confident and hubristic that they lower their standards and get caught for future murders through sheer sloppiness.

Ice agents.

Philadelphia seems to have a new one every 10-15 years. Here is the most recent one to get caught. It is a developing story, We don't even know how many victims yet. For more Philly serial killers, here is a wikipedia list.

Recently saw a short video about this, and data shows serial killers are all but disappearing. The absolute height of serial killers was around the 70s. The reasoning is more about investigations getting better at catching murderers after their first kill, preventing them from ever becoming serial killers.

The percentage of homicides that remained unsolved was sitting barely above 50% last I checked. That number goes up and down a bit but has overall been getting higher over time (worse) since the 1960s.

Your chances of getting away with being a serial killer have never been better. Especially if you target a poor urbanized area and/or minorities.

https://en.wikipedia.org/wiki/Elizabeth_Wettlaufer

For every new bit of technology, there's someone who finds a way to do stuff that the technology would never catch because the inventors of the technology never thought of the idea in the first point. Case in point, Elizabeth Wettlaufer is one of Canada's most prolific serial killers. They in all likelihood wouldn't have caught her if she herself hadn't confessed at some point. She was a nurse in a nursing home who regularly killed her patients by overdosing them on insulin. Because of the nature of her patients, those deaths never aroused enough suspicion to be investigated by police.

Plenty of cops that would qualify

Europe has solved a few long cold cases of serial rapists and murderers by using DNA database data from services like 23andme and Ancestry. They can find someone related to a killer. Legally this violates laws and cannot be used in court, but it gives the police the person to watch to prevent another event.

Serial killers have access to the same internet as the police.