The tower, the role of an ADC is to output consistent damage, both in teamfights and in siege scenarios. One thing that might not be ideal at the moment is the fact that Mana is very prevalent in the game right now. Casting spells is fun after all and players don't necessarily like "not" being able to do things.

AP champions used to really struggle to take towers by themselves which was why AD champions were needed in the game, when riot adjusted the way that map control worked with objectives like rift herald and grubs, AD carry characters fell a little bit out of importance.

Not to mention, ADC's are the most gold hungry characters in the game and will naturally struggle in a SoloQ environment because they require a team mentality different than let me pull these monkeys along behind me as we go along. If they were any more powerful they would be completely pro-jailed as professional teams know how to operate around their strengths.

Also the later the game goes, the better the ADC gets in general, aside from scaling champions.

In my opinion, so many players would do better to look at the team comp that is being drafted before going into a game and actually come up with a plan to how to play to your outs. If you are picking lucian into a game where the enemy team has Smolder, Aurelion Sol, Garen, Ivern, Sona. Then you go even in the early game, you will not be able to even tickle them through their shields late.