Ok, this post is so crazy, that I have to respond further.
Generally speaking, a flash will freeze action so you need not worry about that. If your photos are blurry with flash, you may have missed focus in the dim light since many auto-focus systems fail without good light and contrast.... or you had camera movement..
Flash only freezes movement when the manual is set correctly. End of story. If the poster missed his focus, or had "bad light" , or had "camera movement, it is only an excuse. He does NOT know what he/she is doing.
"most photographers don't know how to shoot manual"
What the hell! EVERY working photographers knows how to shoot in manual mode.. This is perhaps the most inform statement I've ever seen IN MY LIFE.
The rest is the poster prattering on about what LITTLE HE/SHE KNOWS about auto settings.
Goodness... Somebody didn't get a hug today....
I can see that you're probably young, a bit touchy and delight in misreading/misunderstanding what you read.. I'll put my 50 years behind a camera up to your few weddings and say that I may know a few things about the subject although perhaps not as much as I would like...
I see that you have also misquoted comments to try to prove your own point.. I'll stand by what I said in the context I offered it.
If you meter carefully with a good meter at several different spots, measure to your subject to know your focal distance, calculate your DOF and then set your camera manually to the best settings for the subject and available light; you are shooting "manually". If all you do is look in the viewfinder and you're setting to what the camera indicates, you may be setting the camera manually but you are far from "shooting manually". I don't think that this philosophy disparages any "working photographer" who likely adjusts settings using the cameras meter readings and experience. There are many others that I've seen who just line up the needle and tell themselves that they are shooting manually. I don't know which group you are in, nor will I guess..
Perhaps you can serve the Poster better by offering helpful advice and recommendations rather than engaging in inflammatory rhetoric that doesn't seem to say anything different than was posted..