Why can't we have skills, perks, and attributes? I'm using an attributes mod right now and it's awesome.
I disagree that there is any such thing as an attribute that you can't also describe as a skill.
Strength? What would it do? Increase carry capacity, and melee damage for any melee weapon right?
You can have skills do that. You can even introduce another skill set for fitness or athleticism. Let the perks in it increase your carry capacity, arm strength for bows and weapons, running speed, etc.
Likewise for intelligence. What does it do? Increase magicka? Increase magicka damage? Resistance to poisons? What?
All of these things could be in a skill tree similar to "athleticism." Something like "Spirituality" that increases magic damage, or spell effectiveness, magic recharge rate, etc. There's nothing an attribute can do that an appropriate skill tree can't also do.
Having both just makes things complicated, because now you have to figure out how the interact. Which one modifies which? Should I increase strength, or should I increase my sword skill? Generally speaking there's a right answer in situations like that, and there shouldn't be.
There's no such thing as attributes. Humans in the real world don't have attributes. We have skills and abilities. If you want to get stronger, you go to the gym and work out. It's as much a skill as anything else.