Akali's Mark of the Assassin Bug.
Hello fellow summoners.
As you can see in the clip, when Mark of the Assassin is casted from max range, the karma will not land fast enough for Akali to proc the mark with her first basic attack as it should be.
I didn't play Akali that much on season 6 or 7, so I'm unaware of how long this issue has been in the game. However, you could complete the Q, R, AA combo from max range back on seasons 2, 3, 4, and 5.
I would suggest to increase the travel speed of the karma Akali throws, but that's not up to me to decide. If you'd like to help this problem be solved please upvote this thread, comment and share your thoughts below :)

EDIT: Thank you people in the comments for letting me know it has always been this way. Back in the day Akali's E could also proc the mark, which made this mechanic harder to notice and less impactful.
Nonetheless, now that Crescent Slash does not proc Mark of the Assassin, I think the speed of the karma should still be increased to make this mechanic smoother.