If you take it at face value there is nothing stopping you from spreading your points across multiple tree's. But what that does is hinders your progress as currently the loot table, trader quests and progression is heavily favored to specializing into one tree. If you dont you find that the zombie/game progression outpaces your damage output and book progression. The bonus's that come with specializing is a little to over powered and is very much a requirement. Especially at higher game difficulties.
Now this isnt an issue when playing sandbox solo as you can adjust the game difficulty to suit the game stage and progression, which will also prolong the book progression as the loot table is spread across so many variables. But that does not work in co-op unless you create a rule by which no one can specialize and become OP.
Hope that explains the view some of us feel stuck in not being able to mix and match our play style
I play at solo hardest difficult with permadeath and I spread points around. I don't feel the game forces me to specialize. In my current game I focused at first on Strength because I wanted to test out the use of sledgehammer for the first time. But I also needed Parkour for my base design, to I had to spend some point in Agility. This turned out to be good, because I found a pistol early and could spend points on Gunslinger to be better. Then I realized I needed something stronger when cornered, so I started spending point on Boomstick, too, which is convenient since it requires Strength. But then I realized I should be better at shooting with rifles at Bloodmoons so I spent some points at Dead Eye (requiring Perception). I have also spent point on Intelligence for Siphoning Strike, which I kind of regret. My point is, the current system provides me with freedom to build a character that fits the circumstances of the game I play, I am not forced to build a specific character, and it is great fun to ponder what to do and try to come up with good combinations.
I realize that some very experienced players may have this down to a t, that they have figured out that one combination is always marginally better and hence only goes for that combination. But most players aren't like that. Most players are much more inexperienced and/or doesn't play games after having read up on all the details or watched videos that tell them exactly what they should do and how they should play the game. Such players will spend skill points on what they
believe will be best, and maybe based on what they have found in the game. They will make mistakes, they will change their minds, and hopefully still have a very good gaming experience. Like I do (although I have played for a long time yet still refuses to cynically go for the theoretical best combination).
I do play quite a bit of multiplayer, too (I have been looking forward to a new game we will start when summer for a long time now), and then it is more likely we will choose to specialize more (often based on whatever weapon we find first, so if I find a pipe shotgun then I specialize on Boomstick), or we just decide that some should use melee and some should use guns. Anyway, it becomes a bit more specializing and less jack of all trades. But we are not
forced to do it this way. It just makes sense. Not because the game is made that way, but because specializing is a facet of society. It makes sense that some become good at cooking and some at carrying heavy stuff. We do it this way because it is a strategy that makes sense, and it falls natural to us. And if any one of us prefer to mix their points more, then that person may do so. Some people in real life have diverse skills, too.
It is all good and the game doesn't force me to play in any specific way. The way it is set up now, I have freedom to spend exp on the stuff I have done (mimicking LBD) or spend them elsewhere (because, you know, I imagine I read books and can learn new skills from them). I get better because I do stuff, but also have the freedom to choose how my character should progress. And it works well for both solo and multiplayer.
