I don't know. I halfway agree and halfway disagree. We've always had things change. I always found a comfortable niche. Lots of Free Software exists, despite the odds being against them. I almost exclusively use software that respects my freedom. At least in private. The important thing is we pick up the fight. And concerning the services I use, we regularly succeed.
I don't really care for Reddit, or all the people moving to Discord. And their millions of users. All I want is a nice niche with an atmosphere I like. And enough users who are aligned with my interests so I can talk about what I like.
And I think you're right and Lemmy -as is- isn't stopping any trend. Because we can see it's stagnating. It'd have to change to do that. Provide anything meaningful to users that they don't have some place else. Whatever that is, great software functionality, nice people, good content... (Ideally all of that.)