Unless your auto-filled support decides to smart pick a healer, the lane is a nightmare. And 90% of the time he doesn't. You can't do anything from the insane damage and low mana cost they have.
Lux spamming undodgeable E or Karma Q with minimal mana use and taking roughly 1/5 of your ADC low HP is absurd. Not only that but the moment they get a lucky break, you're dead. Oh Lux misses 10 Q, one lucky Q hit you, same with Brand. Nice, now you're either dead or forced to go B.
Now wonder Ezreal is played so much. Almost every game there is a Lux, Brand or Karma bot or is banned.
It makes the lane totally stupid and highly unfun.
Sure you then play safe and don't die, and look at top or mid, what you see ? He feeds like a carrot. Great. You are underfed ADC and die in 1 second and now face a beast.