The winstreak event is optional.

tl;dr the penalty for not achieving 5-0 is minimal.

I know there's a few posts discussing the whingers and complainers already and the intention is not to rant and add to the negative space. But, for the last few weeks most people have complained about lack of content or reason to play the game because it was too casual. Some felt the game wasn't challenging enough, or there was a lack of reason to battle. Some were disheartened that there was no prize at the end of the Expert challenges against the NPC.

If you think about it, the devs came out with a solution: giving a one week optional challenge that gives an emblem instead of a limited drop card. And yes, it's not supposed to be a walk in the park. Why does it need to be?

And if you decide not to play, at worst you miss out on the emblem. The rest of the hourglasses and dust can be farmed without getting the 5 winstreak, so progress is not gated by the event. It's not like there's a Crown Rare Snorlax at the end of the challenge. It doesn't affect your ability to keep pulling your two packs a day, or finish your pokedex. If this isn't the mountain you want to climb, well, don't then.