mustardoverlorddamn straight you'll never play them if you don't watch themwhy prepare for the future if you're not their yet, if you counter the retardation of open that makes you higher then them, and if better then the other team then you should progress and watch a new demo that is your level, once you beat that level you progress to the next. you cant watch something higher then you and expect to apply the same principle to a completely unrelated match similarly learning small things like trap placement and micro gameplay like what to do with uber and where to jump as soldier can be very helpful in your open match but watching tlr, probably the best soldier in invite, wont help you beat the best soldier in open because you aren't tlr and your team isn't mix^.
the invite metagame is just better than anywhere else. sure you could figure out the specific retardation of the open team you're playing and counter it- I do that a lot. however, you also wanna learn how to actually play correctly, how to play proactively and force the other team to adapt to you. if you don't know how to do that you'll always be shit.
tl;dr my dick is bigger then yours, you lose.
Mechanic wise, TF2 is a pretty simple game. An open player can easily apply the positioning, jumping position, heal order, rollouts, etc. of an invite player. Sure whats going through the invite players head is completely different than whats going through the open player, but you don't improve past your division by only trying to beat what's in your division.