You have a huge midgame spike with Irelia, especially with triforce. Tanks don't completely ignore your damage. That doesn't mean you can straight up dive them, but still, you are a stronger duellist usually than CC tanks. Also midgame you can roam, you can kill people extremely fast and are very dangerous.
Another strategy would be to splitpush, since you can take one or two people at once. You can also get botrk to deal with tankiness much more easily. But you'd be very squishy.
Also,
level 1 and 2? Extremely overrated. She becomes stronger at lvl 3+ when she can go for those small free no-counterplay trades with shield, knowckup and stun, meaning she gets 0 damage in return. She isn't that great of an all-in champion pre 6. And she does scale extremely well into mid-lategame, and with last whisper destroys tanks, so she can easily splitpush.