You should have stopped there. Your opinions about how people judge autographs is obviously based on this sentence. If you had experience you would understand how, in most situations, telling a real from fake autograph is quite easy. This knowledge is what experience brings to many, just like in all things in life.
When people ask for an opinion, we give it. I, nor anyone, is obligated to go into details as to why they think an auto is good or bad. Many don't for exactly the reason Steve mentioned.
I find it amusing when people make that statement that they don't mean to offend. They say that as they know what they said is offensive and think that statement somehow makes it less offensive. Perhaps instead of writing it, choose a way to say it that actually isn't offensive. or say nothing if you have nothing constructive to add.
Again, perhaps if you had knowledge about autograph collecting, you would understand that experience can help to account for many of those variables. There are always autos that people do not feel comfortable giving an opinion on because of those situations and we will often opine that we can't tell for sure.
BTW, machines can replicate things precisely. Autopens have been in use since JFK and are able to be spotted often because they are so exact. If you are interested there is a book written in
1965 by Charles Hamilton about JFK's use of the autopen back then.
https://www.amazon.com/Robot-That-He.../dp/B000S3RQ56
Judging autos seems arbitrary to you because you, admittedly, aren't really an autograph collector. If you were, then you would understand that each of us has a method that they feels works for them. Do any of us bat 1000%, of course not, but it certainly isn't arbitrary.
Your two statements here seem contradictory. Judging autos is arbitrary, but wouldn't that make your own opinion the same? Why would you trust the opinion of the least experienced person in the room instead of the most? People come here for opinions as they know that there are many very very experienced collectors and dealers here who will offer their opinion freely. Certainly it makes sense to want to hear their opinion especially if you don't feel you know the signature well.
Just because something can be signed doesn't mean it is. Even if all of Steve's criteria are fulfilled doesn't mean it doesn't have to look like the person's signature. It does. Those loops mean something. If you knew anything about Mantle, you would know that his signature changed in a very distinct ways over the course of his career. Many people can tell a 1955 sig from a 1957 sig quite easily. Once the beginning of the auto boom in the late 70's/early 80's, Mantle took special pride in his auto and was a machine. He could be fall down drunk nearly unconscious and his auto was almost exact.
My father player country music in the 70's and Mantle and Martin would come into a club he played in frequently in Manhattan(O'Lunney's). I have a couple of Mantle autos from those times where he was absolutely hammered to the point of nearly passing out and they look almost identical to standard sig from that era. Again all of this info comes from experience, which you obviously do not have. Just because you don't know this doesn't mean others don't.
This is the exact type of thing someone who knows little about autographs tells themselves to make themselves feel smarter than everyone else. If you knew something about autographs, you would know that it can be very easy to tell bad sigs from good. Just because you can't, doesn't mean others can't.
The take away is that knowledge is power. People here have knowledge and share it freely with pretty much all to all who ask. I think that it is pretty cool that there is a place like this around to help people. I can't count how many people have been steered away from bad purchases by the people in this forum. If you don't think the expertise here has value then you don't have to take advantage of it, but it is rude to ridicule those who offer their assistance freely.