Christianity. When Emperor Constantine converted Rome to Christianity, he began laying out various restrictions on the games including prohibiting it being used as a punishment or even as an option for criminals, forbade the branding of gladiators, and so forth. Emperor Honorius would then completely ban the games, which had already dwindled by then, in honor of the martyrdom of Saint Telemachus. [1]
Most of the time it was not the church that did the execution. The church was more an expertise if you will and delivered the suspect to civil authorities with a judgement.
The civil authorities then did what the law called for.
In the Spanish and Portuguese Inquisitions, this is a distinction without a difference. Further, throughout much of the European history of the Catholic church, the distinction between the church and the executive function of the state was practically nonexistent.
I'm just saying we shouldn't get on a high horse about "death spectacles".
Witch burning ran largely on public sentiment. It wasn't democratic per say, but relied on a community turning on its members, either out of paranoia or jealousy. More akin to a slow and formalized mob lynching than some top down affair.
There have been recent (1990s and later) discussions on televised executions in the USA.
This is not only anathema, but also abhorrent to people who live in countries without the death penalty.
These "death spectacles" are far from ended. There are definitely people who would welcome their return.
Here's a serious analysis from the USDOJ in 1999 named "Televising Executions, Primetime "Live"?"
Its annotation is "This article examines the pathways to a televised execution, including First Amendment issues, principles of open government and victims' rights."
The "news" brings you all the death you want, daily. If you want to try it out for yourself there's plenty of Antifa-type organisations to give it a go. If activism isn't your thing you can join a football (the real type, not that silly American game) hooligan tribe for your ritual combat urges. Still not your thing? Join a gang.
Gladiator 'games' were part of the 'panem et circensis' or 'bread and circuses/games' strategy to keep the populace from revolting against the powers that be. They've been replaced by the above, and more. If the silly plebs still seem to be restless there's always another crisis at hand to keep them down, from climate to COVID to whatever comes next.
[1] - https://en.wikipedia.org/wiki/Saint_Telemachus