I have a 1,4kg Jack Wolfskin Gossamer. Bought it over 10 years ago when I was 16. It's far from the perfect tent, but at the time, it was cheap and ticked all the boxes. I've used it in both winter and summer about twice a year, every year. It's small, light and it just works (although it takes a lot of practice to successfully pitch it in soft deep snow). It's very small, but I can change my clothes in there and even cook in the tent.
I've seen people struggle with bivy bags, and most of them weren't that much smaller or lighter. But most importantly, I know which one I would prefer.