Shelters without forced religious services. Without forced NA/AA. Shelters that will allow families to stay together. Shelters that don't take away walkers and oxygen tanks due to being "weapons". Shelters that are safe, for everyone, especially if you are trans. Ones that allow folks to actually improve their life instead of waiting hours for food and mandatory classes. Bonus points if they provide for pets as well: I know of at least one woman that stayed with an abusive partner because of this. Her only friend in the country (!) was her dog. (He died while she was pregnant, so she got a better life, but no dog).
It is unfortunate that the shelters we do have are rarely good enough.
I don't think society is at a place to do such a thing, but I'd personally like to see everyone getting the option of low-cost to free basic housing. A single person would minimally get a private room and bathroom: More likely a proper studio with a small kitchen. Clean, secure, and functional. Easy-to-clean and easy-to-replace surfaces and appliances. Professional cleaning 2-4 times a year, mandatory.
Of course, I think we should only have shelters for folks that have temporary emergencies and homes for everyone else. People will still need shelter from time to time even in a more perfect world - fires, floods, abuse, money mistakes, and so on happen.
This is all a dream and I don't think we'll get to this point soon enough.