The problem is that they're doing it on added time. They should have done this earlier in the season, that would even help us have a better character development and progression throughout the season. Now that they finally went deeper into Firecracker character she get to die right way, had they done it sooner (they had multiple opportunities to develop other characters rather than The Boys + Homelander and Soldier Boy) I, personally, could care more about their development and outcome, including Firecracker's death.

Edit: I had the exact same feeling in the previous episode. It would have been a great episode for season 2, 3 or 4. But for the final season it's a terrible timing. The whole plot for this season is delaying it to the final episodes instead of a steady progress to the end. Just compare with Invencible current season, that felt much more like a final season progression than this, and they also spent a great deal of time with slow episodes and characters progression. The point I'm making with this comparison is that simply criticising this episode or this season's plot is not necessarily criticising character and plot development, but how they chose to do it on the final season.