Quite a few people used it as a Heroku add-on, where self-hosting isn't an option due to dyno restarts and lack of persistent storage. https://elements.heroku.com/addons/redistogo
Even the notice mentions this, emphasizing that the alternatives they recommend don’t have a free tier.
It has been successful and had its time. To suggest this has anything to do with it having a free tier is to not understand the trajectory of the business at all.
heroku addons:destroy redistogo
heroku addons:create heroku-redis:hobby-dev -a your-app-name
See my SO question for this - https://stackoverflow.com/questions/72695052/migrating-from-...