From the product POV, anyone who has ever used knowledge base will tell you that you should keep everything related to your data/ info in a single app. Spreading them out by any categorization is just inviting recall issue later on.
Tasks in GMail (and IIRC also Calendar) existed long before Google Keep. You are talking about the standalone application of Googles task-system which came with version 3(?). If anything, Google Keep is the problem here. Why was it duplicating features which were already existing in the Google-verse? Instead of integrating with the existing systems and improving them.
There is nothing wrong with spreading out your interfaces and workflows, as long as they all work on the same data. No interface is perfect, so having specialized interfaces for specific jobs is beneficial. But Google is not doing this with Keep, instead maintains another parallel system again.
I have a few recurring Keep reminders, which is a document larger than a couple of sentences that contains line breaks for formatting.
If you were using Keep as a kind of reminders/tasks list, you should switch to Tasks for that, since it's much better designed for that use case.