Hmm. I know some natural stone is more likely to have fissures than others, but this seems excessive to me, particularly where they fabricated the edges. Did they warn you ahead of time of the fragility of this material and the possible outcomes?

All natural fissures and the nature of the beast. You would need to change materials in order to not have any fissures.

The one shown in the photo I copy here is not a fissure. That one is a crack. The line is too straight to be a fissure. A fissure follows the contours of the stone’s mineral crystalizations. That one in the photo is also more widely separated than a fissure would be. It also appears from the photo to have a change in plane on either side, but we’d need you to verify that by running your fingernail on it.

A fissure does not change the plane of the stone. In your OP, the first two of your photos look more naturally occurring with more irregular paths, so might be fissures. Again, run your fingernail over them. The one by the drilled hole could be a fissure that became a crack from the driling - hard to know from the photo.

Cracks can be repaired by a skilled fabricator. Fissures do not need to be repaired.

See how this pic shows the fissures running along the boundaries of the minerals?

These idiots slap a diamond bit onto a grinder and go to town when drilling faucet holes. They're in a hurry, the plug finally lets go, and the grinder smacks into the stone, cracking it. Yes, "cracking" it, not "fissuring" it.

The island corner crack is a tougher call. If it's solid, I'd hit it with a color matched Sharpie (same with the faucet cracks) and forget about it. The only real fix is to finish the break which is problematic with that damned mesh on the back. With the piece free, you can get plenty of color matched adhesive applied and polished. Looks nice, usually can't be felt, and is stronger than natural.

In my previous kitchen I had a slightly smaller corner "crack" in my Taj Mahal quartzite, but it was so well repaired that it took me several months to even notice that it was there. I wouldn't be happy with what was done to yours.