With the right setup, yes. Insulation, electrical, a mini-split for year-round climate control, and a good internet connection, run ethernet or use a strong Wi-Fi extender, make it a legitimate full-time workspace. People do it every day.
The real advantage is separation. Your commute is thirty seconds. Your office door closes behind you, and you're at work. When the day is done, you walk back to the house and you're home. That mental boundary is something a kitchen table or spare bedroom can't replicate.
