I'm a stock-app kinda guy too, but I'm convinced that Fantastical 2 is a worthy deviation from my stance. I do agree with the consensus that Apple may under-develop its stock apps to the degree that it keeps a healthy ecosystem for third-party developers. For example, Nintendo's own games are so good that it gives the impression that most all third party games are crap; Nintendo, in effect, being the ecosystem's own worst enemy for its platforms.
Now I can manage both my Calendar and Reminders with Fantastical 2, and it is my one go-to app for anything date related.
Fantastical 2 does work with both Reminders (and Calendar) in the sense that they all utilize iCloud to populate data in each given app.
That being said, I do occasionally return to Reminders to adjust the position of the Reminders in a given list. But that's about it anymore.