5* can be used fine without constellation. The 4* an equal to default 5* if build right. They need to add the 5* characters to the standard pool little by little so people can up the constellation. When I did played when I get a new unit I move on using that new unit if its a dps.
unrelated 5* note, It doesn't help when they throw beneficial baseline buffs to the character's kit onto the constellation C2/4.
Games content is generous but problematic when the roster continues to increase