I have stories for this!
At a recent SC, I (corp) mulliganed from Agenda flood into...worse agenda flood. My opponent (runner) was a very new player who admitted a friend made his deck for him and he was still learning to play. The runner legworks turn 1 and hits 3 agendas and said 'wow, that must be really lucky!' to which I replied, 'no, that was a really smart play you made, I had no ICE and no econ operations on turn 1, what was left in HQ was worth checking out, and Legwork is perfect for that.'
Was luck a factor? yes. Could I have played out of agenda flood better? probably, but I didn't, and the turn 1 legwork was the right call that my opponent made, and that's why he won.
Another game I was PE on 6 points. Runner is on 1 point and decked (Chronos Project). Runner hits R&D for a medium dig, accesses with 1 card in hand. I had scored 1 The Future Perfect, which is the only 3-point agenda in the deck. I add 2 Snares and a Mushin to sweeten the pot as he commits to access. Accessing any other agendas will flatline the runner, or at least not let him win. The runner access both TFP and wins both psi games.
Was he lucky to hit the only cards that could have won the game for him? yes. Was he lucky to win the psi games? not really, I think of that as a skill play (one I usually win, which is why I play with it).
Luck is a factor in Netrunner, but it's not the only factor. Players have to build and practice their decks to respond to bad draws and work with what they have. What separates the top table players from the players just outside the cut is often the advice to 'play with the cards you draw.' You can't obsess over the cards you don't have and blame them for not being in your hand, you just have to win with what you have.