I think I am quite older than you! Shooting since 1947; scale focusing; no light meter; 1956 some uncoupled Selenium meter but rangefinder; finally 1970 Mamiya Sekor 500 DTL!!
Main problem with Kodachromes was extremely narrow latitude; 1/2 stop was visible but what colors! Saturation very high.
Someone pointed out that Digitals have changed our expectations; indeed! ISO 400 was very fast and very grainy; contrast build up fast.
By the way scanning with ICE sometimes IR cleaning helped on Kodachromes; most of the time horrible artifacts due to silver in emulsion but once in a while it helped; makes no sense.
Back to scale focusing days : in these days of AI; any program to help out of focus? Doubt it but have quite a few.
Oldest Kodachromes are actually 8mm movies 1948 taken by Dad; when exposed correctly (seldom) they are like shot yesterday. Amazingly they have a couple of Color prints given to them by friends back then that look terrific. Do not know how color printing done back then but colors are excellent.
I think Color negative prints came out around that time but what I remember of them was bad fading.
Things have improved!
An old amateur

What I've found is that Kodachrome retains a wider dynamic range than can be captured in a JPEG. I macro-photograph my slides to raw digital files. I don't scan them. The raw files contain the full range of tones and colors in the slide, and Lightroom Classic (or the same ACR controls in Photoshop or Bridge) can compress the tonal range into an sRGB JPEG quite nicely, if you play around with all the sliders. Blown highlights are gone forever, but a one stop underexposed slide can be lightened significantly and adjusted to look better in a JPEG or print than it looked on screen. Digitizing is the best thing that ever happened to film!

Examples follow. Please view the downloads for best quality. Original K64 slide from 1983 was exposed at 1/30 second, f/2.8 or f/4. Probably used a 35mm f/2 Nikkor.

ScanCafe in Fishers, IN, is a decent option if you want a commercial service to do it. https://www.scancafe.com

Current Pixel in Atlanta, GA, is another one: https://currentpixel.com

A lot of the resulting quality depends on the following:

Film stock — Kodachrome slides are always the least resistant to dye fading, probably followed by Anscochrome and certain Ektachromes. However, most Ektachrome slides lose their yellow dye layer first, then the magenta layer goes. Fujichrome slides from the 1970s fade to pink. 3M slides and Agfachrome slides tend to go red.

Storage conditions — Slides stored in plastic or metal storage boxes, BOXED metal projector cartridges, or BOXED Carousel projector trays tend to be cleanest. Slides in archival polypropylene album pages are usually in as good a condition. Slides stored in PVC pages may have severe damage from the outgassing of vinyl chloride from that harmful substance. Slides stored in high humidity may have mold damage. Slides stored with dust and grit on them may have it embedded into the base (glossy) side of the film, due to humidity shifts over the years. Scratches on the emulsion side of the film may show up as colored lines or even clear lines. Scratches on the base side of the film show up as black or gray lines.

Exposure and processing — Slide processes were/are all standardized and — in most labs — rigidly controlled. So exposure at the camera determines the density of the slide (how light or dark it is). Don't expect any improvement in digital images made from over- or under-exposed slides. Most commercial services will try to reproduce what is there, rather than adjust for light or dark images (How do they know what the scene looked like, or what the photographer intended?).

Some duplication services will use Digital ICE hardware and software to try to remove dust and scratches. The infrared sensor in an ICE scanner reveals surface imperfections that the software then removes. Unfortunately, that does not work on Kodachrome emulsions, because those are ridged, layered surfaces. It doesn't work on silver emulsion black-and-white negatives, either. It does work on Ektachrome, color negative films, and chromogenic black-and-white films.

Remember that when viewing old film images converted to digital, our perceptions of quality have changed! It is possible to create much better digital images (sharper, cleaner, clearer, more color accurate...) than it ever was with film.

The difference between a $.50 scan and a $5.00 scan is usually custom finishing — Clean the film, crop for the main subject, straighten the horizon, adjust color, recover highlight and shadow details, set exposure and brightness, remove dust spots, sharpen, etc. There is a lot of dynamic range in film. It can contain information that might be revealed with a careful operator at the controls.

Thank you for the excellent background explanation of slide scanning by a service. I am a Scan Cafe customer and I have been reasonably satisfied with their service. I have had them scan slides, negatives, and prints, in many formats. Their slide scans to digital are exactly as you explained - the image and condition of the slide determines what ends up in the digital scan.

However, my experience with scanning negatives has been different than slides. I have scanned both negatives and prints of the same film images and the results can differ dramatically. Theoretically, a scanned negative image should produce greater resolution with better results. However, I have found that the old film processing labs not only developed film to negatives; they enhanced the image when printing from the negative as part of their base service. They might have performed basic brightness, contrast and white balance adjustments, and even cropping, to make the print. These adjustments were all part of the basic processing finishing, probably automated to some degree, and not customized. Additionally, prints might even have been improved with custom finishing by a skilled operator.

Therefore, I have found that a print in reasonably good condition will generally yield a better digital scan than a negative scan, even though its companion negative could yield higher resolution.