Would a wetsuit be good winter-wear?

They’re good insulation, particularly against water. But annoying and cumbersome compared to good winter clothing for above-water.

Wet suits work well to slow down heat loss in cold water.
On land a wet suit would act more like a sauna suite in which you will sweat heavily.

Wet suits work under water by trapping a little water between you and the suit hints the name wet suit. When the water gets trapped it gets warmed up by your body heat and makes you warm. On land there is no water to get trapped and get warmed by your body heat so it would be more colder then underwater.

Wet suits work under water by trapping a little water between you and the suit

The dry land equivalent is trapping air. Thus the warmth of dressing in layers and thick but light materials like wool, down, and synthetic insulation.

@Call_Me_Jay I didn’t know that.

Only if you are in the water. On Land, dress in proper under layers and get the same effect.

As a first layer I think it would work great. Like panty hose.