>and horribly difficult to focus.
>I don't use autofocus, pretty much ever, so that isn't a consideration.
But it is a consideration. Modern lenses are all designed for autofocus bodies. Yes, you can flip them into manual, but it is still a manual adjustment on a gear designed for computer control. A decent manual focus lens will typically have 270 degress of motion in the filter ring allowing much better control for humans. A autofocus lens typically only has 90 degress of motion (and then infinite turning drek). Much hard to get critical focus manually on an autofocus lens than a manual focus lens.
Also, your older lenses probably weigh much more than the modern lenses. Lots of people prefer the lighter barrels.
I do a fair bit of astrophotography, and the modern Canon glass is great for that. Crip, clean, and no need for focus once truly focused on infinity (varies on each lens, but typically "close" to where it is marked). The older lenses just don't have the sharpness.
So there's a place for each of the older and newer lenses in my kit.