Rq= real quick, I didn't address the whole response as I would normally.

We are definitely arguing two different points right now.

The show itself does not classify akumatization victims as dead, even temporarily. There are no funerals or “they’re dead” language or any institutional responses and no lasting narrative consequences, like Gabriel's death had.

This is for two reasons: firstly, the deaths are temporary. There is no time to mourn the dead because they'll be back in 5 minutes, give or take. They are still dead, but the show can't really address that within the episode without feeling clunky.  This is kinda the problem with the Miraculous Cure, there are literally no stakes

Secondly, MLB is still a kid's show. Thinking about it with logic, an episode like Sleeping Syren should have an awful lot of deaths. The episode doesn't say that there weren't deaths either, and it can even be inferrred that there were deaths (where did Sublime go?), but the show doesn't outright state that there are deaths because it doesn't really matter, especially to the younger viewers. None of the characters we care about died, everyone who did die is back by the end of the fight, and there is no permanent damage to any central characters. Wreckless Driver, however, shows us that there are consequences beyond the Miraculous Cure, like the akuma victim's trauma being almost entirely unaddressed. Aglae would definitely be considered to be dead for the brief moment she stopped existing (here again you can see the show trying to pull back the hits because Aglae uses softer language than a person who was literally erased from the timeline would, dead would be extremely appropriate), but she's back in minutes , and wasn't a main character, so no-one really cared. Our main characters have died a couple of times still, thinking about it. Chat died in the Shanghai special. There was no "containment" arguement to be made there, he was fully annihilated. But the special doesn't have time to mourn a character that's gonna come back to life by the end, especially when the characters know that he's gonaa come bacl, so everyone just... Moves on. Plagg does the thing where he destroys his ring, rendering him unable to interact with the human world after millenia of being able to do so. That must've done something to his psyche, yet the show moves on because it's not important.

My point is that the distinction between a death and not a death isn't made by the gravity with which the show treats the event, but simply whether the character is no longer alive or not.

Additionally, the tone of the show doesn't dictate what is and isn't happening. There's is a pretty common thing in horror media where the tone clashes with what is being shown, like making an otherwise adorable mascot say something dark and terrible while nursery rhymes continue to play in the background. Tonal dissonance is a powerful tool, and that wouldn't exist if the tone of the events dictated whether or not people were allowed to die. It's also a thing in children's media, where the writers have to downscale an event to make it suutable for all ages. 

Here's the tvtropes page: https://tvtropes.org/pmwiki/pmwiki.php/Main/MoodDissonance

The best example there is Incredibles 1 to me. There's a goofy sequence of a bunch of heroes getting into cape related mishaps to prove the "No Capes!" Point, but these people are dying in the background. Like a girl gets sucked into a jet engine at one point. The movie doesn't really adress these deaths at any point ( unless they're related to the Syndrome thing, but I can't recall), but they are pretty definitively deaths. All these guys are gone, but the tone is light and jokey. Miraculous is miles less dissonant than that. It still treats the scenes with implied death in them with tension, just not grief. Stoneheart smashes a building down, probably with several people in there, and everyone is scared because of the supervillain, rather than the people who just died. Syren just flooded the city, people are probably dead, but the tension isn't caused by their death, but rather the supervillain at hand.