I'm assuming that old lenses works differently than moderns once. And you will need to find that settings which will suit your needs and will help to achieve what you want.
Well the result differs from today's lenses.
Modern lenses are designed to offer good sharpness due to digital sensor resolution. Many things have changed. One of the things that have changed is glass. Most of the lenses to today have more plastic (composite) lens elements and less glass. Although they are well designed and met in expensive lenses as well they differ a lot from old lens designs that were made 100%. Glass lenses are very demanding and costly than plastic. Also older lens design are not always designed for optimal resolution in comparison with todays demands. The optical formulas have also been changed since then as well as customer demands.
These and many other factors differentiate the today's standards as well as the lens performance and result. This is why we read quite often about 'vintage look' of vintage lenses in out photographs. The glass design, the optical formulas, the optical properties, the composition of the glass (even the soil used in production for glass) the coatings and element design have changed since the past. So dis the performance.
In any case, even back then there were made excellent lenses designed optimally even with today's standards, but back then glass was the element used.
Anyways, the vintage lenses have their properties and overall performance signature that gives this 'special' look in our photos.
Many great photographers also claim that modern lenses are more sterile missing the 'kind of' character the older ones had.
A long discussion....
Everything is nice depending on what you want to do.
You have noticed in example that my photographic style has a bias towards the dreamy like feeling, the imaginary, atmospheric etc. So for me vintage lenses are tools to express myself better, helping me to achieve the intentionally wanted 'feeling' and express it more clear.