The issue with app apps is that are isolated stuff, we have a single brain, we need integration. That's why I live in Emacs, where org-mode alone can integrate next to anything.
A simple example, jut note about a payable bill due before a certain date:
- we need the bill, for instance a pdf file
- perhaps the email where so send a payment confirmation to be polite
- a note with the date and the amount
- annotating after the payment the payment reference from the bank
- ...
Only in an integrated system such simple task can be done. No isolated todo app can.