If you know counter matchups and the strengths/weaknesses of champs, then you would realize that Irelia’s weakest time is in the early game. If you survive it and get ahead/even with the Irelia then she isn’t gonna be a huge problem. It’s when she goes midlane and takes advantage of the squishyness and low mobility of the champs seen there.
I play Garen against her (when she is picked top) and I win almost all the time. Your q silence fucks her up hard early and with Grasp I can usually get a first blood on her at lvl 1-2 or even when I am lvl 3.
Her damage reduction also roots herself in place, so you can simple wait for her w to go to the full duration or for her to end it early before you hit her with your CC. The only way Irelia can build up her passive (and conq if she has it) is by auto attacking or using q on the minion wave or champ. So to deny her a huge part of her power, poke her a ton early (preferably before lvl 2 so she can’t use her w) then bounce the wave back to your tower, freeze the wave and zone her. She can’t walk up without eating a ton of damage, and it opens her up for a gank opportunity.
Midlane Irelia will usually get Ignite, so if you are a mage then get Barrier. Grevious Wounds doesn’t reduce shields and her damage is low enough early on that she can’t really be able to burst through any defensive spells you have and through Barrier on top of that.
This post is me trying to help you understand why she isn’t as powerful as most people say she is, and giving tips on how to beat her in any lane as any champ. A friendly guide, she is in her right way powerful but she also has very clear weaknesses. If you take advantage of those weaknesses then you can win, which is why most people in low elo complain about her and lose to her. They fail to see her weaknesses and don’t take advantage of them, they don’t realize her strengths and fail to respect them and back the fuck up which means they end up feeding her.