As far as I know, viscose is the same as rayon. For me, rayon has one or 2 desirable features- woven fabrics can have a wonderful drapey- ness that I can’t get in other materials. This is especially good for me for some blouse or shirt styles and potentially, pants, such as a dressy track pant style. I find it more breathable than polyester or silk, but not as comfy or practical as cotton. Its big downside is shrinkage and wrinkling, especially 100% rayon. Have to dry clean or wash very carefully and no machine drying. ( I’ve been able to sometimes fluff in the dryer for a minute, but have also ruined some things by oops, a minute of 2 too long.)
It also is often in a blend, often with polyester. This is less wrinkle- prone so sometimes makes a pant fabric workable and it handles washing a little better.
Also it’s just variable, the fabric. You can sometimes tell in the store, by the squeeze test, whether it eil just wrinkle horribly or be more resistant. Prints and colors and textures make a difference , too. If you don’t mind ironing that can be okay after washing if it holds up during wear.
That all sounds off- putting, but bottom line is, I DO buy rayon or blend items but shop very carefully and try to target the specific benefit, wardrobe- hole the garment will bring, that I can’t get otherwise, vs its fussiness- level and buy only the ones I think are least fussy.