For this use case, a subscription makes a lot of sense. I have no complaints, though I currently do not subscribe to this application. I would, if I felt the need.
My take on the hatred boils down to these things:
Utility type applications built as a service offer an inexpensive purchase of some kind, or are AD driven, etc... Then, features are changed, roadblocks added, user experience degraded to create problems that subscriptions pay to remedy, often poorly.
Noisy subscriptions. It's not enough to send a few bucks a month. ADS, various pitches, in app sales happening, all contribute to what might otherwise be a simple, worthy experience and solution.
It can be hard to cancel. -->if this happens to someone even once, the hate can be visceral afterword. Everyone else, no matter how well they do business is impacted to a degree.
Subscription apps / services going away on short notice. What were people paying for?