Couldn't agree more, Planner, ToDo, Lists, Outlook Tasks (or is that ToDo now?) plus whatever the new thing is coming, what do you use when? Even MS advice articles on that contradict each other. Some integrate with Teams, some don't, but again not in a sensical way, arrrgh!
Planner could have been really good but its basically dead now, nothing on its roadmap - we tried to use it within our team, but our boss likes shiny reporting dashboards, Planner's built in ones are rubbish and integration with Flow (or whatever thats called now) is intentionally crippled so you can't even hack it into a Sharepoint list that can be easily dashboarded with PowerBI.
So we are stuck with our current "method" of putting all our activities into a Shared Calendar on Outlook, exporting that to Excel once a month, and hacking that into the pretty pictures our boss wants to see...