It's not so much that they want Namor to be killed
They're more upset that shyt was written in a such a way that Namor HAD to be killed
Bassett was right about how furious nikkas would be over her death. I get it
Now the reasonable comparison can be made that Peter spared Goblin in No Way Home but Peter is not the leader of a nation so there's that
The problem I'd offer in regards to Wakanda is they haven't really been allowed to kill anyone, which is directly opposed to how they are in the comics. They didn't even kill those soldiers at the beginning of the movie and they SHOULD have.
Meanwhile the Talokan murdered the FUKK out of their soldiers. Overall the Talokan looked more serious, assertive, and about business than the Wakandans did
These things add up and nikkas start getting frustrated and think MCU Wakanda looks weak
Namor didn't have to be killed, because there is war at stake, a war with an equally vibranium-yoked up nation. There was more at stake than a personal beef. The Wakandas where looking like they were about to be wiped out before Shuri showed back up with Namor to end the shyt.
Your logic is all over the place.
Namor's fighters were more capable from top to bottom. Even after Okoye "killed" some of them on the bridge, they got right back up like nothing happened. So your solution is to start a war with these people that get right back up after being "killed", after you've take consecutive L's to them, when Shuri chose a better "play nice" option to stop the Ls.
"but Namor had to be killed"