I've been taking a lot of notes for ~16 years. When you write too many, they become write-only. It's too difficult to sift through them to find nuggets you can synthesize into something else. I've tried structuring my notes after writing them, but this becomes remarkably time consuming and difficult to do unless you are extremely diligent about how frequently you do it.

You've got to structure your notes as you write them, and LogSeq makes this easy.

I still take a lot of notes via "Note to self" in a messaging app; I don't use the LogSeq mobile app because of some opinions I have around syncing (if you pay, you can sync, but I want full ownership of my notes and to trust that they are private). However it's just a copy-and-paste for me, because I've got my hashtag structure figured out mostly.

I have a few tips for new users:

Use hashtags - but not indiscriminately.

It might take you some time to find the "themes" of your notes, before you've really wrapped your head around it you might just pepper hashtags everywhere. Eventually it becomes pretty clear. Use them diligently and later when you get fancy with search and queries you'll be glad you did.

Don't write massive blocks.

Separate larger thoughts in the outliner - sub-thoughts, parallel thoughts. Make child blocks. Remember that child blocks inherent the tags of their parent blocks, so don't repeat tags in child blocks or the search results will get messy. When you come to a conclusion, hide your evidence and reasoning under your conclusion for future reference.

Finally,

Journal!

I am very glad I've been journalling for so long. I wish I had done it more. Every now and then I go back to old journal entries and revisit the me of the past, and the problems I had. I can reflect on them, add amendments, and essentially have a conversation with myself through time. It is remarkably valuable.

My opinion on obsidian

I've used obsidian a bit. It is much more polished and so are the plugins. However, the long-form structure it promotes loses out on the second piece of advice I wrote above: don't write massive blocks. In my opinion, it is much easier to synthesize something later with your notes when you have structured them in an outlier format that is backed by a true graph structure with searchable parent/child relationships. It's more like how your brain works, and if you're using this as a second brain that's important.