I have toyed with several things (ie croc knock-offs, Zems, etc) including nothing or just punching some laces through a discarded insole, but I still keep my slippers as a luxury item/camp shoe, etc. I actually wear them everywhere and any time I'm not in my trail runners, ie. air travel, around town stops, etc. I like the break it gives my feet from being constrained in shoes.
My women's size 8 weighs 5.25 oz. for the pair. For the versatility and use I get out of them, I'm happy with that at least for now.
For river crossings, I just leave my trail runners on.