Thank you for asking, so I will answer you.
I'm by no means, a high level competitor or anything; just basically a nobody, MA hobbyist like most people in here (no matter how important I try to sound to be).
And I'm not implying that anyone's chosen path in the Martial Arts is invalid; just that, training in combat sports is the highest level; with being a UFC Champion the highest, based on this question:
What can the average, ie. Kung-Fu forms world champion guy (who can't really fight well) do, that a UFC champion of his weight class wouldn't be able to, if he really wanted to.
Now if you turn that question around, this all kata guy (even if he sets his mind & soul to it to train for the UFC), is probably going to get demolished at the level, anywhere close to the UFC. Maybe even in the low Amateur stages of 1-5 fights.
Change my mind.
Ok, so there are some assumptions here, so let me speak to that first. There are quite literally hundreds of styles of “ Kung fu”. They vary widely in form and age. Some are focused on technique, some on historical traditional training, some on health and spiritual development, and still others that are based on pure fighting skill and conditioning. Many are a mix of these differing qualities. I cannot speak to every different “Kung fu” because there are so many, there is no way one person can experience them all. My particular martial art has elements of western boxing ( jabs, hooks, etc.) it also has throws, sweeps, takedowns etc. We don’t do competition. We focus on balance, posture, coordination, and conditioning. We have several forms, or kata as you refer to them. We don’t teach any forms to people until after two years of regular consistent training. When we spar that is also after two years of consistent training. Sparring for us was a mouth guard, a cup, and bag gloves. Then we go 2 vs 1 with no rules For 1 minute rounds. I can tell you that there has been blood, and broken bones. I have had 2 breaks myself. I don’t fight on the street, but I have. I don’t recommend that as a training technique. It takes a very long time to become very skilled at what we do. It’s not fancy, it’s difficult, we don’t award rank, we don’t teach children, we don’t do demonstrations, we don’t wear any snazzy uniform or gear, or belts. You won’t get a trophy. My Sigung ( teachers teacher) would smack me for not listening to instructions, sometimes with a stick. My Sifu would pick up people by their head and kicked me in the tail for an improper horse stance. The main difference in “Kung fu“ styles has more to do with the teaching style than technique. That’s the main thing, because it isn’t tailored to a business model, it’s tailored to getting results from the students that can do it. Not everyone can train like this, not everyone wants to. I think it’s important to distinguish this. Everyone trains for their own reasons. We neither encourage nor discourage what individuals want to do with competition. We have had two students that entered MMA competition and both did quite well. Training and teaching style is what makes a decent fighter into a highly skilled one. Some things cannot be taught, which is part of why not just anyone can succeed. UFC has brought a lot of attention to martial arts as a whole, it has shown what works well and what doesn’t in its own show. UFC has also changed a lot since it began. Each of the main MMA formats have their own distinct formulation of rules and requirements. It is important to remember a few things when comparing fighters in a ring situation. First, that floor is bouncy, and people have to wear gloves, this favors a grappling art over a striking art, and almost makes a throwing art obsolete. Second, there are rules about what techniques can be used, for example, no small joint manipulations are allowed, neither are elbow strikes to the back of the head/neck. These are for obvious reasons. Third, there are no old UFC fighters that are still competitive past age 45 or so. It’s true that these MMA guys at the top of the chain are skilled and tough. It’s true that anyone planning to fight MMA needs grappling skills as well as striking skills to stay competitive. So where did they get those skills? Most learn BJJ for grappling but some are wrestlers. Many learned kickboxing, boxing, and or some TMA for striking. By and large, almost all of them trained in some type of TMA at some point. By my estimation, BJJ is TMA, and so is Boxing. The distinction here is that MMA is just that, a mix. Each person puts together skills from several martial arts and pits that recipe against another person. The people changed over the decades and so have the rules and recipes that work in that specific framework. In the end, an arm bar is an arm bar and a punch is still a punch. The framework of rules is where the difference is. The teaching style, and the individual that is training is what makes the fighter. UFC does not create fighters, it promotes them. Teachers and coaches and hard work create fighters. Broad statements that generalize “combat sports” as being the reason for a fighter‘s individual success don’t jive with the fact that no one person has trained with every coach or in every martial art. It’s the man, that unique individual that ends up with a recipe that works for him. I may not have changed your mind, but hopefully that explains my point of view.