Hive is a good position when it comes to decentralized media. Nearly all the clones failed but usually because someone is branching off to have control they felt they deserved. Recipe for disaster.
Twitter will be fine for awhile yet. It's designed to shackle users to the platform. Naturally conditioned to feel like there's a lot at stake or a lot to lose if they leave. Very difficult for them to put it down.
Yes hive is doing great and new features are always being implemented here.
Sure. Like anything though, there are a few issues. Decentralization is hard in general. If someone doesn't like something, sometimes they want to attempt changing everything, for everyone. Easier to build on rather than take off but some are wired that way and want more control than what comes naturally to everyone in a decentralized arena.