I love doing backstroke. For years I thought I could never do a decent backstroke because of poor shoulder flexibility, but then I discovered rotation, after discovering TI. I don't think it puts any more load on the shoulders than front crawl, in fact I feel that it's less strenuous on the shoulders - not that I experience any problems with front crawl, apart from age-related lack of mobility.
I believe backstroke is the ideal warm down stroke after a freestyle or breaststroke session. It also fits in well at the end of a lap swimming session at the pool I swim in, because most of the swimmers have finished their workouts and have left the pool.
My backstroke is slow but improving. It's nice to improve at something in your seventies.