1). It's not pure luck. If the shooter puts it in the perfect spot, the goalie has no chance of stopping it. The goalies generally only block poor shots (not far enough to the sides of the goals, or it is shot waist-high so it's easy for the goalie to dive and block it). Definitely plenty of skill involved.

2). Admittedly it's still an imperfect solution to end the game, so I'm curious if you have any alternative suggestions. I grew up playing soccer and in some of the tournaments I played in, after regulation time has expired and its still in a tie, each team would be required to remove 2 players from the field. This would start to open things up and make it easier to score. Every 5 min or so (can't remember exact timing) another 2 players were required to leave the field. It could eventually end in a 1v1 situation which would be pretty cool, though I never saw it happen.