I think some period drama can be quite alienating, but 'Downton' isn't. This is going to sound quite, um, pretentious, but someone said that it's like a soap written by a poet. ↗
The general view is that actors start on soaps and then maybe graduate to prime-time television or film; normally you don't see a film actor going to do a soap. ↗
Soap opera wouldn't be my first choice, but at this point in my life, I would consider a soap. It would allow me to act and still do other things with my life. ↗