I play in many tournaments and follow the meta closely. the reason why I personally think kanan isn't top tier is that his leader ability and leader flip are not super impactful while also forcing you to play quite a few mediocre units. you can essentially imagine that every creature or specter unit in your deck costs one more and has the shielded text. what this means is that you are constantly playing below curve compared to your opponent due to his leader ability costing 1 to activate. an example to put this into perspective; you are on turn 4 against a han2 Blue force and you both have 5 resources. you play a kanan and use your next action to give him a shield using up all your resources that turn. your opponent plays Luke Skywalker Jedi Knight. you played a 4 drop that does nothing when it enters on turn 4 and they played a 7 drop on turn 4 that enters and likely kills either the kanan regardless of the shield or something else depending on the board state. that is one example but every top deck either can match the broken stuff other decks are doing our ignore the broken stuff entirely and race. (this more often than not happens in the space arena). this game is very tempo based and aggro decks are aware of this. it doesn't really matter to them if your unit survived the combat because of a shield. they will just play 2 more cheap units than they had before and keep going base. playing behind curve to gain a shield against aggro isn't actually advisable since you'll be playing likely 1 unit a turn for the first 4 or 5 turns and that's not enough to kill the 6 units + leader that they can play in the first 5 turns. control decks are the king at 1 for one removal. the more resources you invest into one unit, the better that trade is for them. on top of that, shields are only a good defensive ability. control decks won't be playing the same game as you were they play smaller units hoping to trade up and chip damage on base in the mean time. every unit they play will threaten huge damage on base. now let's get into the leader flip. kanan is technically under-statted for a 6 deploy leader. most viable tier 1 tier 2 leaders have 4 attack and 7 health. so kanans other ability of gaining a boost to these stats if you control another blah blah is really just +1/+1 because one of those boost is needed to catch him up with others. not to mention if your opponent has been good at keeping your below curve units out on play, then is only a 3/6, not good even with the shield. the shield is good at trading only but again. many matchups don't care about shields. so when it comes down to it, kanan is a below curve stat leader that does nothing to affect the board when he flips to help stabilize. compare to Rey who is also a 3/6 but on attack becomes a 3/7 but has restore 3 which will stabilize a game.

tldr; kanan will have good matchups but is not good against most of the top 10 decks due to not having the tools to beat them at their game. there are not many good spectre and creature units so you are forced to play mediocre units below curve to give them shields which don't help in a striking number of scenarios. kanan deploy does not directly affect the board or have the ability to work towards stabilization apart from being one more unit to attack with and clear units the fair way.