Like most content on Twitter, the discussion around it is mostly a loud minority complaining.
I agree that even out of those groups, there are not a lot of people deleting accounts and moving to other places. But, my perception is that a lot of people are indeed spending much less time on Twitter. Twitter competitors are not only Mastodon or Threads. It is also YouTube, TikTok, Instagram, Netflix and alikes, advocacy for consuming less social media overall, etc.
Then there is of course Mastodon and the upcoming Bluesky.
I do feel a bit like "what's the alternative"; I like being an active contributor rather than a passive consumer, so falling back to just reading scraps on the net makes me uneasy.
It can be hard to tell, the published numbers and other people's guesstimates do not tell much of the full tale.
I think many are soft-leaving: using twitter and which-ever alternative they are considering in unison while they see how things play out. Perhaps more than one alternative. People will eventually decide because multiple contact points will be a hassle, at which point we might see a glut of people leaving twitter if one of the alternatives has enough momentum at the time.
A significant problem ex-twitter has is that much of the advertising that left has not returned while user and bot activity hasn't dropped by nearly enough to compensate for that so the on-going losses have grown despite all the staff cuts and so forth. Some advertisers are splitting their spend elsewhere, some are playing wait-and-see like users, and some have just realised that dropping (or reducing) twitter as a channel hasn't harmed their RoI on marketing budget so maybe it wasn't a great channel for them in the first place.
[caveat: I've never actually used Twitter, other than being sent links to threads occasionally and thinking “this is a terrible way to get across an idea worthy of more than one sentence”, so might know nothing – long before the recent kerfuffle I considered it “too full of the sort of people who consider twitter to be a good idea” and from what I gather indirectly it is increasingly home to a lot of the sort of people/content that I already get irritated enough by on other channels!]
To be honest, as someone who doesn’t care about the twitter culture war and still sees a lot of value in the site, mastodon is steadily becoming a better place for actual technical content. Twitter blue checks have insufferable opinions, and I did better when their existence wasn’t forced on me.
i'll have to try it one day
Go for it.
You can buy a Twitter for 44 billion dollars, thats easy - but moderation and user management, not tanking the profits into the red, not killing the brand with weird behavior - these are the hard parts.