Many games that have combos have input buffering to allow easier chaining of combos. Basically the current attack animation allows you to press the attack button before the animation has ended and then triggers the next attack in the combo after the current one has finished. Basically it would remember that you have pressed the attack button before you can actually trigger the next attack and then do so automatically when possible. If the attacks have an "end lag" part (which is often used to tie the end of attacking back to the idle animation if you stop mid combo), this is often also skipped or interrupted to make the combos feel more fluid. Not having this feels kinda awkward when you are used to games having this feature.

The key part is "Minecraft Dungeons".
This project is not trying to replicate Dark Souls.

I have no idea where you got Dark Souls from specifically. There are tons of games that has this feature. I don't know how the combat system is in Minecraft Dungeons, but if you want to make a mod based on it, it doesn't necessarily mean you have to copy it 1 to 1. You can make it even better!

For example, the Bloodstained: Curse of the Moon games are based on classic Castlevania games, but they make the gameplay experience better. They don't try to replicate the awkward player physics from those games.

But of course it's up to you if you end up adding this feature.