The problem isn't they died
it's the execution
Ashura was a YC level fighter that was giving Jack a hard time by himself, and he dies by bombs, something no One Piece fan believes anymore because of Oda, so we spent a bunch of chapters sure he was alive, and now that he is dead we don't feel anything for his death
Izo came in here at the start of the Raid, halfway in the arc, didn't get to do much and was killed just like that.
And then, if this wasn't enough.
Oda reveals their deaths in a chapter that he also puts a funny fanservice bathhouse scene, completely sucking out the sadness and drama of their deaths.
Their deaths had 0 impact because of the execution.