I assume this is basically just the core idea of your game currenly.
Is it worth expanding, or should you abandon this? I dont know. It is hard to say at this point.
For right now this game is dead beat boring.
But, there were lot of things I really liked in this game, and while the current core sucks, I can see how this could become possibly a good game.
So I would say, expand the game a bit more to see if game becomes interesting.
Lets start with the boring part.
Problem is, there is nothing to do in this game. You just keep clicking the same buttons in same order, and it doesnt really matter if you do it faster or slower either.
Oh, and one bug. You can close the gate right when the boat is entering.
And although yes, those boats start coming on queue, there isnt really much control on players side to speed things up meaningfully or anything.
On top of that, with nothing to do, the day lasts really long for nothing to do.
And boats, they come left, right, left, right. So no decision there either. They could at least come randomly from one side or other, and it would be slightly more interesting, although, with current system that would only make it stressful.
One option would be to make this into idle/relaxing game. However, having it take that route, and you actually having to push those buttons, defies the purpose.
Now to the good and suggestions.
The graphics. Instantly I saw this game, I wanted to play it. I was hoping this to be some business game, which it unfortunately wasnt, but still, the graphics made this game much better. They are simply said, interesting, and I would really like more of a game with this kind of graphics.
I also liked how there was this day and night cycle, it added to the atmosphere, and the main character taking a lamp also added to the realism and interest.
Actually, one of the things that I very much liked in this was its educational aspect. I didnt know before they used horses to toll those boats around. Otherwise I was basically aware of the system, but in more modern version, so it was interesting to see how that character concretely did the thing.
So even if the game was not very good at all as a game, as educational piece this was actually pretty great. I could see something like this on display in a museum, where you coull give a try being the gatekeeper yourself. It wouldnt be exciting, it would still be boring, but it would serve its purpose and be much better than most interactive stuff they keep putting. As in, in that environment I could appreciate it already as it is.
So how to make this better then?
Several ideas came to my mind, which however might require throw realism aside a bit.
For example, let there be more than just one of these canals. If there be for example two, then you could choose which one to open etc. And if you then get tolls from boats, you could expand them to hold two boats at once, etc.
Boats arriving randomly from left and right, also would give you decisions like do you wait for two boats to come in first before you close the gate and lower the water for the other side, and risk there becoming too many boats waiting on the other side then. And perhaps you could even direct boats to those two different canals, and they could have some sort of benefits, as in boats would behave different ways.
Naturally there could comes some sort of attacks that you need to defend. Birds flying, click on them to hush them away, or even indians coming, needing you to shoot at them.
And that store, I noticed sometimes crew bought stuff from store. That store and its upgrades could be one fun part of the game. Buy stuff to the store and keep upgrading it etc.
Or then one way would be to make this into something like "Papers, please", where while this is the core of the game, there is more to the game in middle of levels.
Anyway, main ponint being, I could see this game could actually work. Right now it is boring, and chances are it wont work even when adding stuff, but I think it is still worth a try to add some more stuff and see how it turns out, since even I felt it boring, I still feel like I would really want to play something like this. There is definetily something in this, in the graphics.
And I want to highlight once more, I really loved the educational aspect of this game. In that you did a fantastic job.