Bayonet charges were not obsolete, but the killing in war was done by fire.

See, for example: https://journals.gold.ac.uk/index.php/bjmh/article/download/...

By the Napoleonic Wars, something below 10% of casualties were caused by melee weapons. And even that was mostly cavalry, bayonets account for ~2%. The purpose of the bayonet charge was not to kill your enemy, it was to convince your weakened enemy to cede his position after you had already done the killing. The forces rarely fought hand-to-hand and when they did it was notable, usually one side was so weakened and shocked that they fled or refused to charge.