They've had years to make an official app that's anywhere near as good as the alternatives, and they've squandered that time. They bought Alien Blue back when it was one of the biggest 3P apps and basically threw the code in the bin. It's not just that the app is bad (read: worse than the soon to be defunct alternatives), it's that they're literally forcing 3P apps to go away with insane API pricing, whilst saying that's not what they're doing. They said they wouldn't do what Twitter did, and that "API pricing would be reasonable", and in the same breath told Apollo's developer he'd be paying $20 million in API fees in a months time. That's insane.
Meanwhile, navigating the fediverse might not be as "seamless" as the official reddit site / app may currently be, but these places are in their infancy. Apps are already being developed (I know one exists for Lemmy, but I haven't personally used it), that will likely overtake the official Reddit app in months, if that, in terms of not only useability, but functionality as well.
And this is really just scratching the surface about what all this means for the volunteer moderators of every single subreddit, that keep everything running smoothly on their own time.