Why is tristana allowed to terrorize mid?

Players on this forum here are complaining that brand bot should get gutted and that it's toxic playing against him. Care to explain how brand bot is any different from tristana mid? majority of mages are forced to stay under tower and perma afk farm far away from tristanas range (just like brand for bot) under tower til they have a entire full item and they can never move up to tristana 1v1. What's even worse is that tristana is insane high Winrate just like brand, but also has a 10times higher Pickrate compared to Brand. Tristana that shouldn't even be a midlaner, has the HIGHEST pickrate of all Midlaners for 3 patches+ and this is Okay?