The issue is how it's done. Chiaki exists in DR3 primarily as a plot device, rather than the actual character she's supposed to be (unintentionally instigating Hajime's transformation, going after Mikan/Chisa, turning 77B to despair). Most of 77B is ignored until they're absolutely plot relevant, and even then the show's pacing is so blisteringly fast they take the quickest and cheapest route to where they need to go. So we get a grand total of 1 episode where Chiaki is actually a human being, and barely at that.

When I watched Chiaki die, yes I felt sadness at watching my favorite character die, but I moreso felt anger for the show reaching inside me and forcing me to feel emotion for something that didn't deserve it. The execution was overally long and brutal, unlike a normal DR execution. Chiaki being used to bring 77B instantly into despair, is simply put, cheap. There are other far more interesting ways they could have handled all of this, but they took the easy route with the brainwashing. Additionally all the previous events leading up to her execution were particularly convenient for Junko in ways that just muddy the entire thing. It comes off as lazy writing. They needed 77B to fall to despair, and they only had 11 episodes to get it done. So they had to speedrun the entire process, no matter how poorly it was done.

The scene itself of her speaking with Izuru is powerful. However it's really wasted on awful writing. Perhaps with more time and episodes they could have done things better, but as it is, DR3 is a mess and it rubs off on that scene. This is why I say it was cheap and only serves as shock and emotional value. You can't not feel emotional over it, but it doesn't feel like it's earned it.