This is an incorrect way of looking at kata, or at training in general. It's just as wrong headed as if someone said, "if your pushups wouldn't work in a street fight then they're not worth doing."
Of course nobody is going to drop down and start doing pushups during a fight (or at least, I can't think of any possible situation where that would be smart). But we don't do pushups to practice for a fight - we do pushups to develop attributes that would help in a fight.
Kata, in my opinion, can be seen in the same light. While some kata or some parts of kata might contain movements that are useful in a fight exactly the way they are in the kata, that isn't the only criterion we should use to judge the effectiveness of kata.
I've said this before, but I think it bears repeating: when correctly done, kata practice is very useful for athletic development.
What I mean by 'athletic development' is the development of athletic qualities like strength, endurance, proper movement (using the scapula properly, hip mobility, thoractic mobility, breathing coordination, that sort of thing).
There is a lot of focus paid to kata by bloggers and guys working the seminar circuit to discuss the bunkai in kata. Bunkai are basically self defense applications for the movements in a kata - if you've ever trained traditional kata, you know that there are a LOT of movements that seem impractical or weird or useless, and there's a large group of very knowledgeable practitioners who try to unpack the practical uses for those movements - finding a way that those seemingly silly movements can be used in real combat situations.
Now I don't have anything negative to say about anybody who explores the practical applications of kata movements - that's fantastic work, even though I personally don't invest a lot of energy thinking about that.
But what I find interesting in kata is not the applications of certain movements to combat or self defense, but the application of those movements as exercises that develop athletic ability.
- Moving forward and turning in zenkutsu dachi (front stance), especially with turns of various degrees, is a lot like the lunge matrix exercises that athletes will use. You can look at taekyoku kata as a long sequence of modified lunges in varied directions.
- Large circular overhead movements (think shuto mawashi uke) are great for mobilizing the thoracic spine, which will make all upper body movement more efficient and improve shoulder health.
- The opening 9 moves of Seienchin, or moves 5-6 of Gekisai Sho, are great for posture and scapular control.
- All kata, if paced properly and done vigorously, provide a form of High Intensity Interval Training.
I'm sure there are many other examples.
I first noticed this when training for my nidan promotion - I was doing a lot of kata practice (kata performance is a significant portion of our promotions), and I found that my movement during sparring was much better than it had been, and the only footwork/speed drills I was really doing was kata.
I'm not trying to claim that any kata were developed or modified specifically to improve athletic ability - I honestly have no idea if any historical figures had this in mind.
But, when you are thinking about your kata practice, and wondering why certain moves are present or what benefits you can gain from that training, it might be worth thinking at least a little bit about things like how performing those movements can improve your physical qualities, indirectly making you a better fighter, and not just how those movements are directly applicable to combat.