Lately Riot has been giving blitz crank a lot of buffs, and to be frank, some champions will almost always just remain pure solo q.
Some examples would be
katarina: Reason - her abilities are easily canceled by top tier players, champions who resemble this problem
Khazix/Zed/Talon/Rengar, most assassins
-All though zed sometimes sneaks in
For top lane good examples would be Darius, Darius is actually really fucking effective if we are talking about solo q, good damage, okay cc, great team fighter, but from the level of difference pros display when it comes to kiting and layering CC, darius doesn't stand a chance in coordinated play.
Blitz crank would also be on this list of champions who are GREAT for solo q, but will quite honestly almost never be pro viable unless you give him a sincerely very broken buff.
The big reason for this?
If you are a pro player
Why pick blitzcrank when you can just play
They do the same thing while having even more abilities that are just as effective, the only place you can argue where blitz is better, is the fact that blitzcrank has a FULL hook, and follow up lock down to fully isolate targets he captures. However, since blitz crank has ALL his power budgeted into a single combo, their isn't much else he offers to a team fight.
Nautlist: Very tanky, and can activate his passive on multiple targets while spamming AOE
Thresh: Flay isn't that long a cooldown so he can use it at least twice in a team fight, while getting resets on his hooks, not to mention his autos are actually pretty decent damage to compared to other supports
Pyke: an ult that offers insane resets to layer massive damage
Blitz crank is simply out classed here, the reason he shines in solo q, is just largely because of how dumb people play online, even at a chally level u see some really cringey mistakes, that simply don't happen in pro competitions.
The reason i'm addressing this, is for i'm afraid riot might eventually just give blitz crank an out of this world insane buff that completely breaks the champion as a desperate move to make him pro viable.
Riot, Blitz crank is a solid solo q champion, and will always remain that way, he will never be pro play viable, unless you give him a buff that's utterly broken.
That or you gutt the shit out of other hookers to make him look more appealing.