Let me preface this with the fact about half of the games I've played are chicken games, and some of the issues i'm about to state are either known or not really noticed, so here:
1. Chicken can't attack underwater units - Technically speaking, they can but when the chicken is on water or underwater themselves, they can't harm units that are submerged, making amph bots op against them on watery maps.
2. Chickens movement on water is really inconsistent and buggy - Most chicken travel on top of the water, there are some exceptions, like with the cockatrice, which travels underwater. With that being said, spidermonkey, basilisk, and sporeshooter all get slowed down by a very huge margin, usually taking 5 minutes to just cross a lake of water.
3. Chickens can be easily overwhelmed in the early game - So hear me out, the best way to win a chicken game is to get everyone to spam glaives and just kill the roosts before they even start, or to corner them. Some suggested counter to this, is to just put the chicken at a higher level, however this is still a problem even on suicidal.(I also just played a game with 6x wave sizes and still was winning by abusing amphbots and raider spam)
4. Some chicken late game units come very late, maybe too late - Take the chicken spire for example, if it appeared earlier, it would actually force players to get out of their deeply entrenched base and rush out to kill the spires like how people rush out to kill a big Bertha. (on the topic of chicken spires, they do a lot but are hardly recognized due to their silent nature, my suggestion is to make them more dramatic in their firing, and explosion, to alert players to them.)
Solutions:
1-2. Have all chickens(except flying units) just travel underwater - Cockatrice do it, why can't the others? Also allow them to attack units underwater, with the exception of ranged units. Also fix the movement of the all terrain chicken units.
3. Give the chicken an early game riot control unit - Chicken currently can be outswarmed early on, If they had a riot unit similar to the outlaw, it would allow to them to not be so easily overwhelmed, and actually aid in forcing players to mix up their armies and add skirms to the defensive screen. Basically, add a unit to destroy the homogenization of players early armies and actually make them think instead of spamming out the same unit.
4. Move some late game units to mid game - Like i said, the chicken spire, but also i also believe the talon should come earlier. The talon is an air superiority fighter for the chicken, planes and gunships can hold the sky from early-mid game, and often players only focus on bombers and ground support, completely forgetting to build any air superiority for the late game when you will need them.
In summary, my points were mostly made to try and change up the meta and actually force players to play offensively instead of camping out in their base until they die from rocs and blobbers.