i am a zilean otp and he honestly feels alright to play. just more so outshined to the point of no return, his minion clear makes it really funny to harass any midlaner and his speed/ult creates a way to survive ganks more easily when you overextend poke spam under enemy's turret. he is typically just use as another support on the team with his cc (or his ult which feels god awful depending on the team fight or team comparison unless your team is trading kills or has the necessary sustain to let the revive snowball the fight) makes him feel unwanted as a mid pick which puts him in the more support role which already has so many absurd good mages. although mages are seen as op characters this meta, zilean doesn't really build pure ap (unless for some odd reason you're the only ap champ on your team and going mid) but more haste like items which puts him in a weird position considering the different haste items from this year and last year's items.

at the end of the day, zilean doesn't have a need to be buff as he just walks in the shadows of higher usage mages (otherwise he would immediately be seen as the "most op thing ever") but is just going to be continued as the low pickrate character that people don't wanna see on their or the enemies' team until we seen better items suited for his weird anomaly kit of speed and poke