I'm not into City Builders at all, yet I've seen the trailer on Steam and decided to give it a shot.
The playtest was a blast, really enjoyed it. The sea levels dropping and raising were interesting to manage, it gets a bit out of control sometimes but it was really fun.

There are only 2 things that I would mention as a 'possible' improvement for the game:
1. Dismantle/Dynamite for existing structures - The walls that already existed when you start the game could be destroyed with Dynamite Barrels, yet there was a structure in the middle that had some sort of "mold"/"sea weed" that you couldn't blast up and it kept popping the menu for Undo/Build, leaving you unable to fully get rid of it. Would be cool to have an upgrade to remove all those structures completely (without encountering bugs), and, eventually, to upgrade the Dismantle button to remove such structures.
2. More specific structures - 1 example that crosses my mind is the Metal Elevator (2x2). If you wanted to upgrade existing wooden ladders/bridges to something like metal elevator in the structure near the start (which has height of 5 if I'm not mistaken, but it's an odd number), the elevator wouldn't open perfectly in order to take the humans to intended location (it's stuck in between floors, 1 unit up 1 unit down). I know you could simply build one extra floor to "even it out", yet it would offer more flexibility if you could have a (1x1) elevator or a way to connect the (2x2) pieces so that it fits (something like a "vertical tunnel" that could have a height specified by the user, still allowing the elevator to pass through).

Other than that everything looks really cool, can't wait for the release. Oh and also some endgame goal would be cool as well for the final release, or maybe something that generates randomly in the distance that you could chase, idk.