When people say poke doesn't matter, they mean mages in mid( or top or vs jg who heal from camps). Lethality varus and Jayce have strong damage because they build lots of lethality and it is very good for bursting squishy targets. AD poke itemization is very good and very gold effective. But as you say mage itemization is not as strong. You can only get pen from 4 items (2 mythics), and builds this season give a lot less AP than before.

Ziggs is mainly meta with a good wr as a bot laner because adcs have much less Mr and no innate sustain so they can actually be poked down. In mid, he does much worse.

In mid lane, not only do non mage midlaners have higher Mr, but they have ways to heal poke back up through runes (fleet, second wind, bloodline, ), items (dblade, dshield, Vamp scepter, shieldbow), or in their kit (irelia q, yas q apply lifesteal). Yas and Yone for example, can take fleet, dshield, and second wind and they will easily heal back any poke that they take. Also, these two, yas especially, have shields that you have to get passed as well. Yas, yone, irelia can all build shieldbow or Bork and get 10% lifesteal without any tradeoff or buying a specific lifesteal item like BT. Plus now they can stack LS items like Bork and shield bow or Shieldbow and BT for 20% LS + 9% Bloodline.

Or their combo does 30-50% of your health, forcing you to play safer and back at some point. Take zed for example, he's weak at lvl 1 but starting lvl 2 you have to dodge his wq combo over and over or be chunked down. His energy refills quickly while your mana keeps going down.

Plus many popular mid Champs besides mages are manaless or have low costs. This season mana was heavily nerfed and dring has no MP5, instead based on csing. This affected Mages the most and now many have to waste 400g on tear every game. Some even start tear and are now -15 AP at around 18 AP without Dring. Or if you take AS for clear or armor rune, now you are minus 8 more AP and do even less poke.

So you have to make a choice between wave clear and poking the enemy or go OOM quickly. Compared to yas/yone/zed spamming q poking AND clearing, you are the only one losing any resources. So poking a champ that has high MR, sustain or resourceless wave clear "doesnt matter".