No one "freaked out". Rather it was immediately ugly and obviously made the game look silly. There is no argument at all for the visual appearance of the cone being authentic to an on-air NFL broadcast. That observed valid criticism is not "freaking out".
Second, it is not comparable to other UI helper prompts and visual cues which have no affect on gameplay if disabled; to use the cone, you
must know where the cone is, you
must be able to see it, you
must look at the ugly thing.
Specifically, it is very different from Tackle Cone in that respect. Tackle Cone is a visual aid to help new players learn the distances for attempting conservative and aggressive tackles. An advanced user may disable Tackle Cone once he learns when and how to tackle and still succeed at tackling; the Tackle Cone is never necessary to succeed at tackling. There was no analogous usability with the Vision Cone; if you take the flashlight away, you can't see where the QB is "looking" to determine if you will throw an accurate pass, and thus you can't use it.
The mechanic literally got in the way of success in the passing game without offering any immediate gameplay benefit.
That second button tap is the difference between getting the pass off in a tight window and an interception. That second tap is the difference between getting the pass out before protection breaks down and a sack.
If you were using the R-stick instead, that delay is instead mechanically enforced by the significant fractions of a second it takes for you to move your right stick from the face buttons to the R-Stick (because you must press A / X to snap the ball and start the play) then back to the face buttons to throw the pass (because you must use the R-Stick to manipulate the cone first to ensure you throw an accurate pass).
All of this was necessary to achieve the same function a user could accomplish with a single button press the previous year - press one button, the pass is thrown. The Vision Cone added unnecessary steps to achieve the same result as the previous year while adding more failure states (throwing to a receiver not in the cone resulted in a wildly inaccurate pass). The mechanic dramatically raised the skill floor of the game (making the game harder to learn for new players as more steps were required to succeed at performing basic actions) without increasing the skill ceiling (the end result of successfully using the Vision Cone was the exact same as not using it at all the year before; an accurate pass in the direction of a receiver).
For many people that one benefit does not outweigh the many drawbacks I've laid out above.
Compare the vision cone and its drawbacks to every Madden game before or since where all I have to do to throw a pass is tap or hold a face button and it instantly happens. No, my QB doesn't have to "see" the open receiver as with the vision cone, but this control scheme is immediately more responsive (I press one button and the ball is thrown) and immediately more mechanically intuitive (no bouncing back and forth between the right stick and face buttons). In addition, I'm already reading the coverage with my own two eyes anyway, so requiring my in-game QB avatar to also do so was redundant.
To circle this back to the topic at hand - Madden NFL 18 - I speculate that the new Target Passing mechanic will be built in such a way where the game is still playable at a basic level without touching it at all (i.e. it may not be as dramatic departure from face button passing as the name implies), but the best players will leverage the new mechanics to throw their receivers open, throw back shoulder fades, etc. etc. in ways which were not possible in previous Madden games. Something which pushes the game more towards the easy-to-learn hard-to-master direction the game has been trending the past couple years.