Just from a quick look at https://fediverse.observer/, it looks like the Fediverse is mostly steady at 1-1.25 million monthly users (give or take) over the past two years with a slight decreasing trend. I think there are some reasons for this that are not entirely in our control.
There seems to be a global sentiment of disconnecting from social media and the internet in general. So, I wouldn't be surprised if ever platform is seeing a decaying user base. Anecdotally, among the people I see in real life, there is a general sense of exhaustion with online spaces. Whether it's from corporate-own, enshittified platforms to even places on the Fediverse, the people with whom I interact tend to find the entire thing hollow. They've trimmed down to one or two platforms (if that). In fact, I've even started to get that way. In the past, if someone were wrong and arguing against a point I made, I'd engage, especially if it's in something that I have expertise. Now, why bother? There's no use arguing; people have little interest in admitting fault or engaging in good faith (again anecdotally). That said, I'll concede that the Fediverse is a bit better on that front, but not by much.
Then there's the alternative nature of the Fediverse. It's been rehashed over and over about how "difficult" it is to get on and use. It's not actually that hard, but the barrier to entry is an extra step. That small extra step frightens people away from even joining. The only time that barrier gets broken is when a "legacy" social media platform does something anti-user. Then there is a refugee wave that comes in and goes out leading to a modest durable increase in users. Recently, there just hasn't been a major controversy on a major platform that leads people here.
Now, my final thought on this is to ask: Is a small and steady-ish population (despite modest decay) actually bad? In my view, I don't think it is. Being smaller and with a smallish barrier to entry means that we exclude a sizable number of the low-effort population. So, there's less (no zero) slop here. Plus, discussions, when had in good faith, can be much deeper and less filled with stupid low-effort jokes. Overall, I'm not too concerned with the number of people on the Fediverse. Growth isn't necessarily the best thing. Even so, with the way most mainstream platforms are going, it's inevitable that they will do something stupid that drives more people to the Fediverse at least for a time.
TL;DR: The monthly population is mostly steady with a modest decay. Most social media is likely seeing similar trends. I don't think the smaller userbase is that bad of a thing.
I study AI, and have developed plenty of software. LLMs are great for using unfamiliar libraries (with the docs open to validate), getting outlines of projects, and bouncing ideas for strategies. They aren't detail oriented enough to write full applications or complicated scripts. In general, I like to think of an LLM as a junior developer to my senior developer. I will give it small, atomized tasks, and I'll give its output a once over to check it with an eye to the details of implementation. It's nice to get the boilerplate out of the way quickly.
Don't get me wrong, LLMs are a huge advancement and unbelievably awesome for what they are. I think that they are one of the most important AI breakthroughs in the past five to ten years. But the AI hype train is misusing them, not understanding their capabilities and limitations, and casting their own wishes and desires onto a pile of linear algebra. Too often a tool (which is one of many) is being conflated with the one and only solution--a silver bullet--and it's not.
This leads to my biggest fear for the AI field of Computer Science: reality won't live up to the hype. When this inevitably happens, companies, CEOs, and normal people will sour on the entire field (which is already happening to some extent among workers). Even good uses of LLMs and other AI/ML use cases will be stopped and real academic research drying up.