Thank you, happy to hear you enjoyed the dog and chopping the vines!
Yes the cave was intentionally very dark by design. You got the flashlight right? As you're about to enter the cave the dog runs off and barks continuously to alert the player of another item. Which is a flashlight, it makes the cave portion quite trivial to complete if you just hug a wall. Multiple play testers said the lighting with the flashlight was adequate, and I personally tested it on 3 different monitors, as I know some will appear brighter than others. However I was still worried it may be too dark even with the flashlight.
If you didn't get the flashlight well... From a game design perspective, the dog slowly introduces these mechanics and the game hard blocks you from progression. By the time you reach the cave I felt these mechanics we're communicated well enough to allow the player to attempt to progress without the dogs help if they felt daring enough. Worst case I assumed they would get turned around, and hear the dog barking, then end up retrieving the flashlight.
However all that said, somewhere along the line I failed to deliver the experience I intended. Next time if I'm worried about a mechanic I will err on the side of caution. That would be a more wise approach. Greatly appreciate the feedback!