Immediate full coverage is going to be difficult to achieve......sorry. The landscaper was correct - few conifers will establish in heavy shade and with that much root competition, especially ones with any size on them to begin with.

Aucuba japonica, Japanese laurel, is a very shade tolerant broadleaf evergreen shrub. It will grow in almost total shade and is relatively drought tolerant. But it is probable that the largest you could find to plant will only be about 3-4' to begin with and you will have to be patient while they grow. Getting them enough water to begin with will help establishment and encourage more rapid growth. But it will be a few years until they reach a height to provide much screening. They can get 10-12' eventually.

Another option is bamboo. Don't freak out! I am referring to a cold hardy clumping bamboo, like one of the Fargesia species. Clumping bamboos are very well behaved - they do not spread aggressively like a running bamboo, but remain in a controlled clump like a very large ornamental grass.

Fargesia is very shade tolerant and will take temps down to 0F. Again, you will need to provide adequate water while it is establishing, perhaps for the first couple of growing seasons. The advantage of a bamboo is that it will already have some serious height to it - you will likely find plants available that are already 6-8' tall - and it puts on height rapidly. Once established, new canes emerging will grow rapidly to the full mature height. Depending on the species, Fargesia will grow 8-20' tall.

Thanks! I am intrigued by the Fargesia suggestion. Can you tell me anything more about it? Is right now a good time to plant? Do you plant right in the ground, or in a long planter? Can I plant them all right in a row so there are no gaps, or do I need to leave spacing for growth? Does the look of it change throughout the year?

Oh and do you know how wide they are/grow to? Wondering how close to a fence it should be planted.

Spring is a fine time to plant them and they can go right in the ground. Each individual plant/container will slowly increase in clump size, so you do want to allow some spacing to allow for growth. And that includes some space from the fence as well. In my climate, these plants look pretty uniform all year long but they can drop some foliage in cold winters.
Fargesia clumping bamboo

A bamboo retailer I spoke with said their tallest plants are about 4 feet. They said only one place in the country sells them at a larger size, and they aren't quality plants. Does this sound correct? I really wanted them to be 6-8 feet when purchased.