Can we address MF

Does anyone else find her kind of toxic now a days? Like in any game that a MF has been on my team or the other, she does really well. Teamfights all she does is press R and with her Lethality build, she shreds the other team to the point where the team fight is over. If you are caught out in her ultimate, you really get destroyed. She is a safe champion, you can't catch her because she gets a speed boost, you get out poked should you try to approach. ADC shouldn't feel like duelist champions.