To my thinking the Mission of the Day could be (and sometimes is) a good device to keep players engaged in the game for a longer period of time; after all that seems to be the goal of "Mission of the Day!"
As to "poorly thought out" I would point to a criteria like "7 critical hits in a battle." I believe, because I for one have done this, it can subvert good team play. We know we can choose ammo to specifically get a critical hit. Most often critical hits are low damage hits whereas playing AP or APCR gives us higher damage with a better chance of taking out an enemy tank. Well, I play for a very specific time period and when that time period is almost up and I'm a couple critical hits short of the goal I'll start banging away with HE. At that point I don't care whether or not I win, I just want to finish off the Mission. Good team play–no, it ain't! Am I the only player to do this? I doubt it!
As to "poorly implemented" I'll use today's "7 critical hits in a battle" REROLL to "15 critical hits" I was 5 critical hits short and in my last battle of the day so I was in a light and tracked a heavy, I then continued banging away at the heavy's track until I had 5 critical hits. Then I moved on and did something similar to a medium for 2 more critical hits. So, with 7 critical hits in the last battle of the day I figured I was successful in completing the mission! NO LUCK, the 7 critical hits where apparently counted as TWO. This REALLY BURNS ME UP because the criteria was NOT 15 critical hits on 15 different vehicles, it was plain and simply "15 critical hits." So, WG, fix it: either state 15 critical hits on 15 vehicles OR fix your counter so that it counts EVERY critical hit.
Source: https://www.reddit.com/r/WorldofTanks/comments/ysmmmw/mission_of_the_day_poorly_thought_out_poorly/