I wanted to thin out the rose bushes to prevent disease but rose bush at the base and beyond appears grayish and dead. This bush is less than 10 years old. We do have black spot issues and I wanted to also clear out any dead leaves etc to prevent this problem. Is it too late for this bush? I am not opposed to pulling it and starting again with a new bush.
No. Old wood is often covered in gray bark. There are green, living, growing canes growing from that apparently dead wood. If there are canes which are gray, dry and dead from the bottom up, including the upper growth, of course you should prune those out but any green, “turgid” (plump, full of sap) canes are still productive and should continue producing the results you’ve become accustomed to from the plant.
Don’t give up on your rose yet. You have 2 good looking canes. Cut out the totally brown dead canes. Nitrogen is your most important nutrient. Fertilize it with something where the first number is the highest on whatever fertilizer to help push some new growth. And water of course is the most important ingredient.