Mobile champion vs immobile champion (Getting caught out)

Something people at my rank need to understand, is if you are somebody like Brand or Morgana, you cannot get caught out, you cannot be out of position, you cannot lag behind to poke. You will die, like... instantly. You need to understand that if you are choosing to play an immobile champion, especially a squishy, you cannot go everywhere you would otherwise go on say Shyvana or Ezreal. Because you just don't have the escape to deal with it.

For example, Shyvana can push a lane out safely much further late game than Orianna, because Orianna has no escapes and will get destroyed when an enemy looks at her.

Gnar can lag behind his team and poke with his Q and autos, because he has escapes and some tankiness. Soraka should not be, she should be as far from the enemy team as possible and not hesitate in just running away.

This isn't so much an angry post as it is an informational one. Not hating on anybody. Just in my rank(Silver 4), people pick immobile and squishy champions then keep sticking their neck out and waiting for Darius to chop it off.