Learn to use the brush and preset soften skin

This preset just means, set the sliders to adjustments that might be used to e.g. soften skin. LrC does not detect skin areas as such automatically: it will apply adjustment to anywhere you paint. Maybe you are retouching green skin, a manufactured product, anything. But you do have quite good control over where you paint plus there is selectivity by colour or tone, as I mention below.

Painting precisely where an adjustment is wanted, and only there - can be quite hard and slow to do.

A faster strategy is to paint rather loosely over an area, and then to erase out of this area with a smaller brush, parts you don't want to soften - for example eyes or lip line. Hold Alt key to erase on the fly (Option); if you have a scroll wheel mouse that's a fast way to change the brush radius as you work, but there are other ways too.

As an aid to either painting or erasing there's an Automask checkbox in the brush settings. With this active, LrC will paint or erase within the brush extent, respecting its size and softness, but only if "similar" to whatever colour's found at the very centre of the brush circle. When you drag the mouse around with the button down, a series of brush-centre samples are taken so the kinds of "similarity" being painted onto / erased, keeps changing as you go. This can give a blocky result sometimes.

So what I would recommend: set the brush size fairly large and soft-edged, turn on Automask, find a representative bit of skin colour, then click and release mouse button. This makes a single "dab". The selection made within this is smoothly related to how similar or dissimilar the pixels are, to that single centrepoint. Make your next "dab" in a new place. It's quick to build up a very nice selection this way. You can immediately undo just the latest dab if you don't like the result of that, then keep going.

Of course whatever way you've painted can then be further tweaked by erasing parts or by adding more parts, either with or without Automask. For example if the skin tone / hue is quite varying, but the e.g. eyelashes or whatever are of a fairly consistent colour, painting right over the skin then using Automask for erasing out the eyelashes or whatever, may be the better strategy.

LrC masking has the option to restrict the scope of a local adjustment to not only where you've brushed / made a gradient or whatever, but also also to certain tone or colour ranges ONLY within that brushing etc. The e.g. brushing can then be done quite loosely, plus that selectivity on what is XXX coloured - as YOU have defined XXX, be that very specific or more vague.

Here's a good start for you:

https://helpx.adobe.com/lightroom-classic/help/whats-new.html

https://helpx.adobe.com/lightroom-classic/tutorials.html

... otherwise ... Google is your friend 😉