To make everything clear because this sometimes kinda escalated lol
1) I don't hate anyone because they run, I occasionnaly run myself as it can be a good stress releaser
2) I know how hard running is and what a good cardio it gives you
First of all, we have to agree on what we call "cardio". If cardio is only measured from a "clinical" standpoint, where they look at your resting heart rate, your left ventricle strength or whatsoever, then, yes, running is great. Even among endurance athletes, runners have the better hearts (the difference isn't as big as some believe it to be though)
https://www.nytimes.com/2019/04/03/well/move/heart-health-swimming-running-exercise.html
Of course, studies haven't been made on guys who would replace their 1h of running by 1h of non stop steady shadowboxing, heavy bag, wrestling drills etc. but let's admit someone who would run 3* 1h a week would have a "stronger" heart than someone who does that type of martial arts adapted training for the exact same amount of time.
With that being said, having the "strongest" heart because a physician tells you so doesn't win you fights. What we generally call "cardio" is also about movement efficiency, relaxation etc., things that come with muscle memory and proper technique. As I said it before, who do you think is gonna gas first in a fight between your typical mid tier UFC fighter and Kipchoge (marathon world record holder)? I bet you it's Kipchoge, because he would be so uncoordinated it would take him three times the energy of the UFC guy to perform the same move.
To sum this up I would say this:
Take Fighter A and Fighter B. Fighter A and Fighter B are the exact same guys, same height, reach, weight, experience, etc.
Fighter A trains for 3 hours a day and runs 1h after that. Fighter B also trains for 3 hours a day (doing the exact same training), but instead of running afterwards, he puts in one hour of steady shadowboxing, Dutch drill, bjj and wrestling drills etc.
Let them do that for 2 years.
After those 2 years are over, Fighter A and Fighter B fight each other.
What I think is that fighter B would show better "cardio" than Fighter A. Because the "stronger" heart A would have got from jogging would have become irrelevant compared to the extra relaxation/smoothness etc. that fighter B would have got from all the adapted cardio. Not to mention he would have less wear and tear on his body than Fighter A, especially if our fighters are bigger guys.
Of course, there is a state where you will become so proficient from a technical standpoint that you will no longer benefit a lot from working on your technique. If you're Floyd and do the exact same sport since you are 5, you ain't becoming much better from a technical standpoint, so work more on your cardio. But when you have to be good in wrestling, bjj, fence wrestling, kickboxing, muay thai and boxing, I don't think you can afford that to that extent.