Unfortunately only content. I spent some time subscribing to similar Lemmy communities that I had on Reddit and many of them just don't have the content yet and I can't exactly generate it alone.
You could make the absolute best software platform (not saying Lemmy is it, it's somewhat buggy), but if people don't adopt it, it won't succeed.
The "winner" is often not the best platform either. WhatsApp is popular but kinda shit, same for Instagram, Tiktok etc. Threads might win over Mastodon for a Twitter replacement, just because it comes from a huge entity like Meta and people can use their existing accounts.
Unlike Twitter, Reddit has not yet fallen off the deep end where using it on e.g old Reddit on desktop computer is a terrible experience. I think the upcoming months will show if replacing mods etc ends up biting it in the ass.
With Boost finally closing, I am without Reddit on my phone. I'll have to see if losing the "let's browse Reddit a bit on my phone because I'm bored" option does good things for my mental health and daily life overall.
Then you don't remember what search was like before Google. Google changed the game and was for a long time so superior to Altavista, Yahoo, Ask Jeeves etc for search results that it became the defacto search engine.
Of course, eventually it all goes to shit and Google is getting there by serving more and more ads across all their services.