I'll just offer the opposite view, for sake of discussion because I think the design we have is quite smart.
Hiding fences with trees - by going through the forest - for me too, makes the exhibit look nicer. Obviously if you build without demolishing trees you might have gaps that cause dinosaur problems, so really, the smart thing to do (imo) is demolish the trees first, see your fence right and then replant.
That means your good looking exhibit costs you more dollars to create (makes sense) and also leaves you with a security problem (fences through woods are harder to inspect). So I get where the OP's coming from but I'm not sure it's 'better' than what's in the game now.
I actually think there is a misunderstanding here.
You can still hide your fencing in the treeline, the highlight is only visible while actively placing down the fencing. This only saves time, your enclosure will still need to be adjusted with regards to which dinosaurs you intend to house. The monetary cost for demolishing the frees is trivial, the real issue is its just annoying and really isn't contributing anything gameplay wise. If I make a large exhibit for a T-Rex or something maybe I want to clear out the area to make something like the T-Rex Kingdom in Jurassic World, but if I want a smaller exhibit for Troodons or something, I don't feel like clearing the whole area to rebuild. Moreover, if I am just going to replant the trees anyway, I don't really see the purpose. The fencing automatically removes trees in its path anyway, I see no point to continuing to have to tear the whole forest down only to automatically plop them back down. Its not like there is some extra gameplay I get by replanting trees, there are no incentives or penalties at any point that might cause me to reevaluate how I build an enclosure just a very annoying and tedious element to get one up and running.
I would further argue that a better exhibit will cost you more to build regardless. Moreover, the gameplay you want to promote is centered around the mechanics and the consequences of the actions arising from using those game mechanics. Building a fence through a forest and just barely failing to connect it isn't inherently fun or interesting. Its basically you made a mistake and are punished not because that is a gameplay mechanic, but simply because your vision was obscured. A lot of people don't like to clear out the forest as well since it looks more natural to be building around it for their enclosures. The point I am trying to emphasize is that failing to completely enclose your dinosaurs is not a meaningful choice or decision its one the result of simply not being hyper attentive to a something that is expected to function hassle free. That's where the real problem with it is, you are losing time trying to make a basic and expected function work when that time could have gone towards more important tasks you had waiting for you. Park failure is just a part of the franchise; however, the faults in my park should be based upon real decisions I made not because you missed this tiny gap in the fence in dense forest.
The emphasis should be on breakouts not: "Oh, there is a small hole in the fence I didn't enclose because I couldn't see it. Moreover, constantly shifting to and from the map is an unnecessary step just to confirm the fencing is fully enclosed. I understand that you are to pay for your mistakes in the game and that you are given so many tasks to juggle to try and cause something to fail. However, placing down my fencing is not an interesting decision unless I am specifically trying to do something unique with its shape. A gap that occurred because it was obscured by forest isn't a worthwhile decision its just a silly oversight that could have been completely avoided by having a simple highlight while placing it down.
I apologize for the length of this response, but I felt it necessary to really dive into how this currently adds nothing of value to the game, but it does cause frustration and tedium. There are other ways to make creating better enclosures a decision making process, but this truly is not one of them and its not enjoyable to do either.
