Is it your settings? LOL CRANK EM UP!!!

Most likely due to the EXTREME over abundance of them. Some areas are SSOOO heavy with trees, they were painted in and have lots hanging in air. It seems some areas that were great with scattered trees, have been over seeded with lots of them. To remove 50% of the trees from the heavily forested areas, it most likely the best thing that can be done. You can have trees scattered but still providing coverage for bases. But this is so much different than I remember about 2 yrs ago. Best be thankful they are not high res, if that's even an issue. LOL
I know the redwood trees have been taken out, but maybe fixing an issue with them or in the area is reason. From the 50/50 ish area to the mountain with the big cave used to look better. Now it's so thick it makes it useless due to the amount of work to remove the area to even get a good look for building.
Please stop overseeding EK!! I'll help cut them down :)

I have everthing on max :P

Pretty sure it's just the old assets then. lol

This mod was posted 2015. A LOT has changed. It's really hard to remove those kind of assets and replace with newer ones given the quantities already on such a large map. I believe The Center came next for him

So until he deems it worth the time to change out on this old of a map, we might just have to get by with any assets. I know he's trying to find the time to work on it again but would be a spare time kinda thing as he is full of obligations. ;)