Both Steve McKichan and Jamie Phillips have gone on record saying this:
A significant workload specific to our position is reading what is going on in front of us is based off pattern recognition.
IMO:
At a higher level, when skaters have good fundamentals, shots/passes/etc are easier to read. Generally, the team defending you is also more adept at identifying and eliminating high percentage scoring opportunities.
Conversely, at a lower level - skaters with suboptimal skillsets are going to reflect in their body language - making reads difficult and/or chaotic.
ie - maybe their stickblade and eyes show they're aiming top corner, but their hands/hips/skates are in position to send it it 5-hole.
At the pro level for goalies - IMO it's not so much the physical ability, but the mental acuity to consistently prepared for all lanes to the net.
It's different for a skater playing down as a they are dictating the play and forcing the defense to react to them.