I tend to think of a deck’s skill cap to depend on how linear the gameplan is. The more linear, the less skill is needed.
Let’s take 2 decks as examples:
Quest(pirate)warrior is considered a low skillcap deck. This is because of how linear the gameplan is. There is little room for flexibility. Basically play pirates and then get juggernaut online if your opponent isn’t dead yet. Most of the pirates determine your curve for you.
Now look at Garrote Rogue. This deck has way more flexibility. You can play it several different ways depending on the matchup. Sometimes you play for tempo and win without the combo. Sometimes you play for a full on combo. Sometimes you have to shuffle bleeds and hope you get there. There are other lines and I’m oversimplyfying of course. The curve of this deck is a lot harder to determine. It isn’t always clear how and when you are supposed to allocate your resources.
Control decks are usually considered high skillcap as well. This is because you need to make sure that you use your resources, removal in this case, in a way that doesn’t leave you high and dry if more threats come down. That doesn’t mean that all aggro decks are “Brain dead” there are a lot of decisions that go into some. Vs control you need to make sure you don’t overextend and apply constant pressure. In an aggro vs aggro mirror things can get tricky when deciding how and when to trade.
In every matchup skill comes in when you are trying to determine if you are the aggressor or the one on the backfoot.(search ‘who’s the beatdown’ for an interesting article on this)
When I think of skillcap, the main thing I think of is how diverse a deck is in its gameplan. The more flexible a deck can be, the more skill it takes to pilot.