Why Tank Meta and how do you counter this?

More specifically to the point... How are you supposed to take down a level 9(in-game) Mundo with Mogs and Tenacity boots(literally these 2 items) who is able to still kill 2 out of a 3 man gank? While I wasn't ready to give up the fight, Mundo repeatedly maintained his onslaught until the game ended.

I was laning against him for the first 10 minutes(where he then started to destroy and out farm me completely) and even though he kept harassing with his Q and on top of that using his E which does ridiculous amounts of damage(fyi he didn't have a Mog at this point, just buildup items for a mog and a boot). Once he had completed his Mogs and Tenacity boots at 10 minute mark he literally kept on diving me under my turret and killed me and still makes it out with almost 1/4th of his health left. I was playing Irelia and I stunned him under my turret while this fiasco was taking place. I later got some assistance from my Jungler and mid laner, but it was in vain... He managed to kill both me and the jungler and almost ended up with a triple if my mid laner couldn't flash away in time.

So far I've not seen any sort of moderation going into this stupid meta that has been going on for almost 2 seasons now... This was but one example.

Off topic: I'm playing support mainly and 7 out of 10 games I manage to assist my carry to win the lane by 5-7minutes so we can start roaming, but as of late this is getting harder and harder with the recent patches (the new patch 8.7 further solidifies this and I have to be even more aggressive to earn my gold than ever before. So aggressive that even my carry can't keep up with me at times...) and the reign of tanks still running solid. Despite all this, there's that one guy in the enemy team (surprise surprise! it's a tank) that ultimately ends up with the win. I'm not expecting every game to be a win, but when you do so well(even beyond that) and for one guy to shatter everything with just 2 completed items is just saddening.

Would like any suggestions in regards to combat such picks from a Support main or a Top main's perspective...

-Thanks-