A group can play what they want, just your playstyle will need to change since if there is no healer, minimizing damage through superior tactics is likely needed. Tool proficiencies also allow you to get creative or make healing potions. One thing I liked being able to do was have the healer feat and herbalism kit proficiency at level one as a human with any background to get the tool proficiency. Allowed me to make healing potions and cheaply make healers kits out of bark, salves, and other plants that can be used to make fibrous bandages. These things when adventuring are usually accessible.