I now have 200+ accounts in my Password manager. Sure, I know I'm part of the 0.01%. But I can't imagine that there's anyone who does own a smartphone but still has less than 10 online accounts somewhere :) You just need them for too many basic necessities of life these days.
It shouldn't be so much of a barrier, and if it is, they probably need help even with setting up Signal or Whatsapp too. After all that requires a google play or apple account to install from the store too.