One of the best things about reddit was looking for answers or other users with the same problem as you, and since Google didn’t really help with that anymore and instead insisted on giving you business results, the best practice was to put your search terms in followed by ‘reddit’ and you’d find your answer.
They’re getting indexed, but search rankings are so low they’re buried. If you put
<search term> site:<server>
you get post results. For examplelemmy site:lemmy.world
You can also put site:lemmy.* and it’ll pick up some too.