Signal, Skype Lite and Facebook messenger all support their own chat, SMS, video and audio calls, SL can be used also as regular dialer, not sure about some niche features like location sharing since I don't use them

if you want to reach most of the people then I guess Messenger would be safest bet

social circle of writer of this article must be pretty small, since it implies ALL how contacts use iPhones and nobody use Android, otherwise I see pretty HUGE disadvantage of iMessages which are not available to Android users