Nonsense. Projection may be the best way to view slides, assuming a decent projector and slides that haven't deteriorated over time, but you can't share them. This is why people digitize slides and negatives, not to mention the fact that you can clean them up and adjust for things like fading and color shifts before they get any worse. This is a picture of my mother taken in 1974 in a hotel room in Boston at the time of my college graduation. The original was taken on High Speed Ektachrome that was push processed to ASA 400. The camera was a Nikon FTn with a 50mm f/1.4 lens. The slide was photographed with a Nikon D810 and a 55mm f/2.8 AF Micro lens over a traditional light box. (Three 6000K fluorescent tubes inside.) I photographed it RAW and did some adjustments in Photoshop. I could tweak it further, but I'm satisfied with this, and the JPEG file will not ever color shift or fade over time.

Nonsense. Projection may be the best way to view slides, assuming a decent projector and slides that haven't deteriorated over time, but you can't share them. This is why people digitize slides and negatives, not to mention the fact that you can clean them up and adjust for things like fading and color shifts before they get any worse. This is a picture of my mother taken in 1974 in a hotel room in Boston at the time of my college graduation. The original was taken on High Speed Ektachrome that was push processed to ASA 400. The camera was a Nikon FTn with a 50mm f/1.4 lens. The slide was photographed with a Nikon D810 and a 55mm f/2.8 AF Micro lens over a traditional light box. (Three 6000K fluorescent tubes inside.) I photographed it RAW and did some adjustments in Photoshop. I could tweak it further, but I'm satisfied with this, and the JPEG file will not ever color shift or fade over time.

Good approach! I use live view with my setup for extended sessions. It works great. But so does Panasonic's DFD autofocus when copying film. (It sucks for action photography, but its the best for still life, motionless subjects like copy work.) I am using a 30mm lens at f/5.6 (equivalent depth of field to f/11 on full frame with a 60mm lens).

Here's another sample image. This is an outtake from an album cover job I did for John Stanfield, a very talented 12-string guitarist from NC. I made it on Ilford Pan-F in 1976. Best viewed on a 4K monitor in download mode. (Original enlarged using Lightroom Classic's Photo Enhance Raw Details with Super Resolution.)

The album is Carolina 12-String. You can hear it on YouTube. Original recording is on Philo-Fretless Records.

I finally got started on my long awaited project of digitizing a dozen or so trays of slides dating back over 50 years. I was stimulated because my 50 year anniversary is coming up and one of the reels is my wedding and honeymoon.

I decided to use good equipment: Nikon D750, micro Nikkor 60mm 1.2, Nikon ES-2 adapter, and process them in Lightroom Classic.

Took the pictures outside in fairly bright sunlight, shot RAW, manual focus, AP at f8 so the shutter speed ranged from 1/40-1/320.

The slides were in good condition considering their age and the color shift on most seemed manageable. Side note – they were mostly almost all Kodachrome, Ecktachrome, Agfachrome, and a number of purchased slides. The most color shift occurred in the commercial slides followed by Kodachrome & Ektachrome, and the least (by far) with the Agfachrome...nothing significant but interesting.

In camera they looked good, in focus, and sharp but after importing them into LR I was devastated. I knew it would be a bit of work getting the color, balance, and light correct but the focus was awful; soft and fuzzy! Sharpening was impossible.

Not only was I not able to get them sharp they weren’t even passable.

I took the adapter off and took some shots with just the lens and they were fine.

What I did not do was shoot them as jpgs. Should I have?

I have attached two originals.

Any thoughts and suggestions, other than use an X-brand scanner or different equipment would be appreciated.

My Kodachrome slides dating to the 60s have remained stable over all of these years, but surprisingly, so have my Ektachrome slides. I'm shocked when people send me scans of their Ektachrome slides and other slides from different manufacturers that have degraded severely. Mine have not. My high school track coach (1960s) sent me some boxes of slides that had turned completely red and asked if I could fix them. I did the best I could and got some viewable images out of them, but there is only so much you can do with material like that. (Converting them to black and white is an option. Playing with the neural filters i Photoshop to recolorize them is another.)

It is a tedious process, but not terribly complex. You should bet able to get acceptable results with your equipment.
But do more testing. You mentioned that the lens alone gave better results.
The ES-2 is only compatible with 4 Nikon lenses (1 Dx 1 Z, and 2 AF-s 60mm micro Nikkor f/2.8's the ED and the D) Each of those requires a different adapter. You describe your lens as a 60 1.2 ? is that a typo?
Is your lens in fact one of the compatible lenses? Do you have the proper adapter for the ES2?
Those would be the first questions to answer.
If your lens is NOT compatible with the ES2 but focuses to 1:1 you can just shoot on a light box.
In any event you should use controlled lighting of known color (you are trying to correct lots of different color casts)
It could be a Good LED photographic light source, or electronic flash.
You spend your time setting up a controlled setup, so once dialed in, you can then do them fairly quickly.

Shoot RAW for maximum flexibility in correction. Find one good dead sharp slide, and work with that to dial in the setup. Remember, film in cardboard mounts is rarely flat so a lot of light and a smaller f/stop will help. Be sure to focus in live view. By tethering to a computer you can see large results in real time. You can also build a couple color correction presets to get you in the ball park quickly.
I hope this helps