I feel like its kinda shitty how overcentralizing haki has become. Like pre-skip, haki existed, but you can still make do without it. Luffy even beat multiple opponents with haki.
But now we're in the post skip where for whatever reason, its impossible to do serious damage to kaido and big mom without advanced haki. Not even if you shove a sword in big mom's neck and emit shockwaves that damage her body from the inside out, can you do serious damage without haki. Its kinda BS tbh.