You are spot on, George. The fitness industry pushes people in two directions: Either it is "stuff you'd recommend to a 60 yo obese person", or it is the hardcore boot camp class that wears down your joints and body. The fitness industry does not do a good job of filling in the middle between the two extremes.
You are also right to be concerned about kyphosis. Most people at the gym are doing exercises which will only exacerbate their kyphosis. Try this: go the gym and just watch people. In almost every exercise, you will see people are rounding forward in their upper spine. For example, watch people doing Burpees.
I wish I had a good solution for you, but I don't. I have been working out daily for over thirty years. As I grew older, I knew I wanted to conserve my joints and I wanted to do absolutely everything I could to avoid kyphosis (because I find it so unattractive). So over the many years I have gradually created my own workout that is between the two extremes mentioned above. However, in a comment like this, I can't communicate to you the numerous exercises I do. If we met in person, I could show you (I live in Portland, OR).
Perhaps my best advise for you, is look for a personal trainer. I'm not talking about the 23 yo at your gym who is getting paid minimum wage. I'm talking about the people who charge $70 an hour. Before you pay them money, ask them questions about Kyphosis. Make sure they know more about the topic than you do (most will not). Ask them if they have read any recent research papers on the topic, and then ask what journal the papers were published in. If they can't give you solid answers, move on to the next trainer. I wish you luck finding qualified help.