Not considering the costs of hosting infrastructure for downloads, developing Fediverse integration in software is an extremely complicated task, and retrofitting it into existing software is no joke.
A more realistic starting point is probably to follow them on Mastodon, ( @Retromags@mstdn.plus ) interacting with their posts and trying to spread them, and to try to build up a fediverse presence for them. Then eventually, if they find that they get the majority of their interactions through the fediverse, they might consider merging their comment sections.
I'm amazed at how fast this place has grown since the first time I saw a Lemmy instance (way before Reddit API drama), or since the first time I snooked around Mastodon (before Twitter exodus) for that matter. So I guess I'm inherently optimistic by the fact that where newer users might see little activity as a bad sign, I see a little activity as a huge improvement on what the status quo was not so long ago.
On a technical side, open source projects also tend not to benefit from growing too fast. It seems to me Fediverse platforms currently have a healthy activity level for the stage of completion they are in. Lemmy certainly grew faster than it could handle for a while, and arguably Mastodon suffered from the same.
The main reason I'm hopeful about the social web is, however, that it makes no sense any more to create a new platform that does not support it. No matter what kind of social networking site you're making, proprietary or open, you're going to want to make it ActivityPub enabled, simply because it gives you a user base right off the bat.
And furthermore, it encourages the development of new platforms, precisely because you don't need to establish yourself with a whole bunch of users. According to fedidb my platform of choice, PieFed, has 124 active users right now. It would not have been a very interesting corner of the old web.
I don't think the established user base here is going anywere, and I think future developments will feed into the ecosystem. So I'm pretty hopeful. But it is going to take time before all sorts of niche communities have made themselves a federated home.
Bluesky and Threads will fight it out over microblogging, while Mastodon will stick around as a smaller less corporate alternative. A year from now people on both platforms can probably follow my Mastodon handle anyway, so I don't really care all that much.