Have you forgotten about making the first event of each month short and straightforward? This is the 4th month in a row where we've had 1 week to play 2 sim weeks. I don't know what other people (who might be able to play every day) consider short but I think that 2 weeks of gameplay definitely counts as either a medium or a long event, depending on how much micromanagement of Sims is needed.
Perhaps it's also worth mentioning that I chose to sit out last month's achievement challenge after doing some research and realising that it was the same event as the mid season major event from 2019 with the only significant change being that this year we only had 1 week to complete it instead of the 5 weeks that people had for the 2019 mid season major. I don't see the point of starting events where I'll probably only get 1/4 of the way through, so I decided I'd rather sit out and do something else with my leisure time. I considered bringing it up at the time but I was super busy during that week beforehand when the rules of the achievement event were open for feedback and by the time I was less busy, the event had already started (so I concluded that it was too late to give feedback on it). But looking back at the achievement event now, I can see that 4 of the participants included comments related to how lengthy it was. Perhaps the team needs to reconsider what actually counts as short...?