I had one of the giant Mac Pros from 2007, and I was able to change drives, RAM, and even replace the included graphics card when it fried. I even fixed my first Macbook pro from 2006. My more recent Macbooks haven't needed repair before the OS was end-of-life.
Personally, I don't miss it, as I'm 100% laptop. If I was into PC gaming, I'd probably have a desktop, but I prefer the simplicity of consoles.
FWIW: Most people who buy laptops are buying at a price point where it's "not worth it" to repair.
The current Mac Pro offers upgradeable storage, and PCIe slots (but they don't support video cards). The CPU and RAM can no longer be upgraded. It's also tremendously expensive, $7,000 for the base model. (That 2007 model started at $2,200!)
I miss it a little. I have a 16GB MacBook Pro that I wouldn't mind adding more RAM to. But I think it's a worthwhile tradeoff for better performance, size, and power consumption.
Personally, I don't miss it, as I'm 100% laptop. If I was into PC gaming, I'd probably have a desktop, but I prefer the simplicity of consoles.
FWIW: Most people who buy laptops are buying at a price point where it's "not worth it" to repair.