The grouse moor is basically a grouse farm. The moor is periodically burned to promote the right kinds of growth, 100s of grouse are released and nature like birds of prey somehow end up with a shorter lifespan.
In any case, I will cede the environmental case to local ecologists. But if it's already farming of grouse, that seems less intensive use than farming of sheep, as an outsider I would be interested in learning more as to why grouse moors are preferable to sheep land. It seems that grouse moors would be far more amenable to rewinding. But as I said, I only have my non-expert opinion!
I agree with you and would rather not see grouse moor turned to solar farms. I'd love to see more moor rewilded, the work that Moors for the Future is doing is amazing. Grouse moors are very much touched and managed though. Gamekeepers seek to minimise foxes, stoats, raptors and trees.