> I've ironically lost more money the more closely I've paid attention to my investments
Without insider knowlege market investments are pure gamble. The best you can do is to bet randomly. Once you deviate from random bets because you are mistakenly think you know something then your investments will underperform.
> Even if you think you know something, you are, at best, still being random
Technically true. But somehow in practice you are random in worse ways. Psychology of most people makes them generate very bad randomness.
But you are right. What I said is just good first approximation. Sometimes you can do better. For example listening to most popular financial influencers and doing exactly opposite of what they recommend gives slightly better returns (it was researched). I don't quite remember if better than fully random though or just better than following their advice.
That isn't guaranteed, because if so you can always do the opposite of what you think and you will overperform. Even if you think you know something, you are, at best, still being random. Anything perceived decrease in return from taking actions is itself just chance (and confirmation bias), because otherwise you could inverse it.