Canelo can't beat GGG easily, because his footwork isn't quick enough to avoid GGG"s attack. Canelo is more of a James Toney type of boxer using the Philly shell and Mexican style, he's a flat footed counter puncher, more then a quick footed Sugar Ray Leanard style counter puncher.
What Canelo is banking on is that, GGG starts to age in one of their last 2 fights and he's able to get a close 1 or 2 point victory.
Canelo isn't naturally big and strong enough to simply trade and take solid power punches from GGG.
Mexican style fighters put extreme amount of pressure on you and nonstop attack to the body and head, to beat them you need a great defense, quick footwork and solid punching power, along with a great body attack and solid conditioning and abdominal training regiment.
Canelo has all of them except 2, conditioning and quick footwork, without those 2 he's not naturally big enough to beat GGG on a natural level.
If Canelo was a natural big middle weight that could actually move up to light heavy weight like GGG can, he could stand and trade and still outbox GGG, but Canelo is just a lighter weight fighter, who could only handle the weight limit of 160 and that's it, he's unable to move up any higher then 160 and be effective at all against other champions at the higher weight classes, just like Floyd could only move up to 154 pounds and not actually even make 154 pounds to be at 100% effective.
Remember that GGG has been fighting at middle weight sense being a Olympic champion and amateur boxer and Andre Ward was a light heavy weight as a Olympic amateur boxer, these fighters are naturally bigger boxers fighting at a lower weight class that strength isn't a problem for them. A boxer that's fighting at middle weight and light heavy weight as a teenager, is very strong and can still make these weight classes at a older age, has an advantage of natural strength and size.
A fighter like Canelo starting off as a amateur at around light weight, isn't remotely a naturally bigger boxer.
With this disadvantage in strength and size, you will need a higher level of either boxing ring IQ footwork and a unnatural God gifted reflexes and super human quickness and hand speed and chin to be able to beat someone like GGG that easy, like Floyd beat Canelo, so easy in their fight.
Anybody who's thinking that Canelo is going to put on a Floyd boxing clinic against GGG is just banking on GGG"s age and decline of reflexes and skills.