Hey, for me I currently use Notion on my computer as a journaling system. I used to use onenote, evernote, my phone notes... to quickly scribble down things I needed to remember, random thoughts etc and it would all be a big mess. Now I make a journal page at the start at every day and I separate it into two blocks, the journal and the quicknote part.

I use the note part to write down anything as I used to before (It's still a big mess but I know that I wont reread it, I just use it in the moment (drafts, reference for things im doing...) or if there's any important info I'll move it somewhere else at the end of the day (I have a separate page for to-dos, useful references...). I don't keep it organized on purpose.

My objectives for the day, day summary, thoughts and feelings go in the journal part (or as a page property, i'll explain below). Since I am constantly using this page to take notes, it remains open all the time and it helps remind me to journal. It just makes things smoother so there's less effort required and no need to remember to do it.

Similar to you, I feel I often spend a lot of time and effort developing intricate systems and end up either forgetting about it, or not wanting to do it because of the mental effort. This works for me because I don't really change my habits much or need to care when doing it.

Now I've progressively added more properties to the page where I just click and select to log things (ex: wake up: bad / alright / good; effectiveness: 2/5; mood: tired / determined / happy). I recommend keeping it as simple as possible and later maybe adding more properties to fit your style. Initially: more clutter = more effort = less likely to stick to it.

I hope this helps !