I prefer older manual lenses. To method give better subject separation. This is partly because manual lenses have fewer lens elements on average, and one of the reasons for this simpler design is the lack of autofocus to get better light transmission. Their ability, and the "side effect" of this, is that they are much better at reproducing space, perceiving depths. Multiple lens elements are ultimately at the expense of light transmission, and each additional optical element adds two refractions to the entire system.
Remember there is a huge blind spot on the retina where the optic nerve is connected to it, and on the other hand, we can only see things really clearly in the area called the yellow spot. The blind spot, as well as the blurred image areas, are already restored by the brain, which generates the "seen" image (complements the information in one eye with the other). If you want to find your own blind spot, just cover your left eye with your hand and look with your right eye at the tiny little dot in the picture below for approx. 20-40 centimetres. The larger, moving black dot will disappear from time to time - this is when the projected image will appear in the blind spot of your right eye.
In the same way, different areas of the brain are responsible for the illusion of 3D image perception, for example (remember, the retina is only 2D, and the sense of space requires the mixing of signals from our two retinas). Over the past two decades, brain researchers have identified more than 30 sectors in the visual cortex of the brain that are responsible for compiling "final" vision information and making the amount of information they receive manageable with appropriate simplifications. According to physicists, the reality seen with our eyes is 1) on the one hand, mostly the product of the brain; 2) since it can detect only a negligible part of the electromagnetic spectrum, it only returns a fraction of reality (this slice of reality is evolutionarily useful, so the human eye has evolved to sense it).
So the human brain doesn’t really need photos that are completely free of optical distortions and colour defects, since you never get that kind of information yourself. There is only one lens element in the human eye (not say 12, with aspherical and other pieces). Our brains can feel more lifelike and realistic if the sense of space and atmosphere are closer to what we perceive through the eyes anyway. For a better visual experience, we may not need full filtering of chromatic aberration or correction of barrel distortion, but real depths.
Because of the above, I’m not at all surprised why Petzval lenses, which otherwise produce scandalous image quality by modern standards, impress us so much. Somewhere it is still closer to the reality we perceive than "flat-ironed" photos (not to mention that the images and memories recalled in our memory go through even stronger distortions, while the brain recalls the "stored" information back into the visual cortex).
People sometimes worry about the sharpness of a lens and then upload their pictures to social media where it is impossible to tell how sharp a lens is. Other factors like bokeh, contrast, colour etc are easily visible even at smaller resolutions on social media. Because of this I think that the overall rendering of a lens and its creative imperfections are more important than its sharpness. I wouldn’t say that old lenses have better character than new ones since this is all a matter of personal taste and lens designers pay more attention to smooth bokeh today. But there are certain looks you can only create with older lenses. Added to this they can be very cheap and you have a huge choice between thousands of lenses ranging from exotic ones with lots of “character” to some of the very best lenses available.
There are even 40-year-old primes with better image quality than many modern lenses. Of course progress has happened in recent years but still affordable primes are often sharper than very expensive modern zooms. Old lenses are usually beautifully built from nothing but metal and glass which makes it a joy to handle them. They can last a lot longer than modern lenses which are full of electronics and very complex designs, both of which make them more likely to fail.
They also hold their value much better than modern lenses. With some patience you can sell most manual lenses without a loss but with new lenses you can expect to lose 30% in the first year.
Manual focusing can actually be very enjoyable. This certainly depends on application but personally I enjoy working with fully manual lenses a lot more than with any AF lens and I would choose a good manual focus lens over an AF lens (almost) any time. You have to do everything yourself. You have to think about the aperture and set it manually. You have to focus manually. Some people don’t enjoy the process at all but I find this process aids the creativity.
So are manual lenses any good? For me the answer is “Yes, they are they are the BEST lenses”.