Maybe. OTOH, the decline in identified serial killers tracks with the decline in identifying the perpetrators of killings period, as the clearance rate for homicides has dropped. Plenty of room for serial killers to hide in that:
https://www.theatlantic.com/magazine/archive/2019/10/are-ser...
https://www.discovermagazine.com/the-sciences/what-explains-...
Also: video games. Young men, who commit most of the murders, spend more time playing video games and therefore less time murdering.
But it also matters what we mean by "solved" too.
I do remember seeing the luka magnotta documentary on netflix (don't fuck with cats), which while not quite a serial killers, comes close to someone who liked the attention.
Most of the (solved) crime news I read about, I'm always confounded how unaware criminals are about "tradecraft".
For an example of stupid criminals, I remember reading in the local newspaper about a group of guys that had robbed a store of phone cards (the story is a bit old) and tried to sell them back to said store.
Instead of using a public phone with one of those cards, they just used their own mobile phone to contact the store. Since in France you're required to give ID to get a SIM card, I'll let you guess how long it took the police to find the robbers :)
Most burglaries and robberies are performed close to where the criminal lives. They are mostly opportunistic crimes done criminals with no thought at the time of what they are doing and no fear of the consequences.
The stereotypical version of that is the drug addict doing anything to get money for their fix, but generally it's associated with not very smart people who do stuff and do not fear the consequences.
https://www.20minutes.fr/insolite/2359379-20181023-belgique-...