It feels like the game has various complexity layers for the player to understand based on how far ahead they're planning and playing. The problem is that it's hard for new players to understand even the first layer, the combat, and the tutorial/UI isn't quite good enough at getting new players on the right track.
First, there's the basic combat layer, which is all about breaking vulnerabilities. You gotta learn what actions work the best together for breaking vulnerabilities based on your current Chosen and what the combat consequences are for breaking those vulnerabilities. That's not easy to figure out from a casual glance, and requires understanding the underlying mechanics of the game. On top of that, this is the crux of the gameplay and it's most complicated element, but the tutorial doesn't seem to be doing a great job helping players understand it very well at all. I think a big part of that is, like you said, that the tutorial doesn't start on day one, it doesn't cover multiple days of gameplay and EE choices, and it gives players a champion without first showing them what it takes to unlock and use a viable one -- or what even constitutes a viable one.
Next, there's the day-by-day layer, which is all about EE and trauma. You have to plan for getting as much EE and trauma as possible, as quickly as possible, and you can only get EE by handling your combat correctly. FruitSmoothie's guide helps explore the issue of day-by-day planning in a way that simply isn't done by the currently included tutorial or guides. There's an element of viability in certain upgrades over others, regardless of your Chosen, and it's honestly pretty easy to miss those high-value choices because their impacts are obscured by the game's own obtuse mechanics. On top of that, I don't remember ever reading about the events on days 15, 30, and 45, or how important the EE injections from those events could end up being for any given playthrough. So, on yet another layer of complexity, players sort of get shafted.
Lastly, there's the loop-by-loop layer, something you only find in campaign mode, and something I haven't even personally started on yet. If I understand correctly, it all revolves around using specifically trained Forsaken to bypass the limitations imposed by standard champions in order to speed up the process enough to beat the reduction in days... which is a whole 'nother level of planning that I haven't even gotten into, and requires understanding what you want your Forsaken to do before you even start corrupting a Chosen into one... Oof.
All in all, it's just a very complicated game, and the tutorials/guides provided just don't actually... umm, guide. They're more like really thorough mechanical explanations, something you might find in a software's help index, rather than practical introductions to the game.
