There is good kung-fu and bad kung-fu. The same is true with all martial arts. You can spot the difference when you have enough experience.
I disagree that kung-fu in general is messy or sloppy. If you're seeing unfocused strikes and movement that seems like it's weak and uncoordinated, then you're probably watching poorly done kung-fu. And there is a lot of that! I could mention one particular popular chain of Shaolin kung-fu schools that come to mind.
Each style of kung-fu has its own standards about what passes for good technique and what does not. In Southern styles, there's a slight lean forward in most stances. But in Northern styles, it is stressed that one must remain upright and not lean forward. But both systems say that looking down at the ground is bad form.
One of the most technically well documented styles of kung-fu is Contemporary Wushu, which is broken into two main sub-categories: Northern and Southern. There are very precise standards developed for each sub-style, and judges need to have a good eye for these details. To get some idea of what I'm talking about, you can watch this video:
The IWUF has a number of videos teaching Wushu technique:
Here's a book you can get that goes over Wushu Taolu:
So suffice it to say, kung-fu is highly technical and involves very precise, coordinated, refined, full body movement. At least when done well.
One thing you might be picking up on as a student of Japanese karate (Shorinji Kempo) is that there is a fundamental difference between karate and kung-fu in the way they are performed.
To many karate students, kung-fu looks unfocused and not very powerful. That's because in karate, your movement is often relatively simplified and done in short, focused, choppy bursts of power. In kung-fu, the motion is more complex and much smoother. Most kung-fu techniques do not involve sudden bursts of power. Techniques are often circular, more graceful, and more complex or complicated.
Why is that?
Well the reason is obvious if you understand what's going on in your forms. In both karate and kung-fu forms, the techniques are all self-defense techniques. In other words, this is what you do if someone grabs your lapel, puts you in a side head-lock, grabs your wrist, holds a knife to your throat, grabs you in a bear hug, etc. These are answers to common self-defense situations that are still valid today. It's mostly grappling technique, not striking, even though everything looks like blocks and strikes.
I go over this more in my answers here:
Name and meaning of stance where you stand with fists on hips?
Why is more time dedicated to exercises and very less for sparring? Is it for the fee?
Now, if you've ever seen Brazilian Jiujitsu, Judo, or Wrestling, do you see them using sudden bursts of power every two seconds like you see in karate? No. Things are more smooth and coordinated with the entire body. Leverage is the key. When you're trying to put someone in a Kimura lock or trying to throw someone using seoi-nage, it's not going to look like a sudden choppy motion. It will look smooth and continuous, often involving circular motion. This is a dead give-away that grappling is happening.
Karate is done the way it is done for stylistic and cultural reasons. But it came from kung-fu. Because it is done with sudden, choppy motions in short bursts of power, everything looks like a strike or a block. Everything looks powerful and focused, short, simple, and direct. And so to a karate practitioner, kung-fu looks kind of weak and unfocused. It's hard to even tell where one technique begins and one ends. Perhaps this is what you're noticing.
But make no mistake. What is going on in kung-fu forms is the same thing that's going on in karate forms. Except, in kung-fu they make it much more obvious that something besides blocking and striking is going on.
In kung-fu, kicks and punches are practiced on punching bags and focus pads. The same is true of karate. If someone has a weak punch or kick, it means they're not doing this training. You don't learn to strike by practicing forms and kicking and punching to the air, in other words.
In kung-fu, sparring looks similar to karate sparring. That's because in both cases, you're doing the same thing. There's no grappling going on. If grappling is allowed, then you're going to start seeing movements that resemble what is done in the forms.
Hope that helps.