Some features missing

By the way, if Subject is really really bad, try Object instead

I think you need to question your sources of information, I think you need to look for better tutorials.

And as for specific presets.

I cant seem to use local specific changes anyore, the subject is selected, with half the background and there is no real way to correct that or select a smaller spot.

Well as to Subject mask. Yes it needs work, but it is not all that bad. Obviously some photos may work better than other.

As for corrections, Their is the Add and Subtract buttons, and you can use various brushes when accomplishing that.

Say I only wanted the stuffed bear on the left

I can select to Subtract, I then choose one of many brushes, in this case Brush

note, that my screen capture skills caused me to  loos the cursor in the above capture, so I edited it in (looks a bit abnormal)

So, easily fixed

 Finished mask

One vital tool seems to be missing. (Amongst other useless changes) I cant seem to change one single color  in the photo. In 2019 I could do that, simply with a slide

Ok, new way, very simple, some learning curve

But, if you want the old way, it is still available, simply change the method selection

One vital tool seems to be missing. (Amongst other useless changes) I cant seem to change one single color in the photo.

This feature is not missing. Use the new Color Mixer panel in the Develop Module. Its in there, click on Mixer to get that tool. Although, honestly, the new Point Color tool not only does all of that plus a lot more, in a better interface.

Other changes, far from useless, add great value, I'm sure most other regular LrC users would agree.