> Having 90% of registered accounts inactive with only 10% of them actively using the platform isn't exactly 'alive', 'growing' and 'healthy'

That's not at all true. Account activity follows the Pareto principle. It's not at all unusual for any online service to have a large number of inactive users. Perhaps it's different for Twitter, but considering I've probably signed up for it three times and use it approximately never, I'm skeptical.