Skill casting system?

Hello, I have played a bit of LoL in the past, now I'm back and I see there are a lot of changes, one of them baffles me:

I remember that some of the skills were like this: [skill shortcut button] + aim + click; Now they are like this: aim + [skill shortcut button]?

Can this be reverted? How is this called and when was it introduced?

Thank you