what I'm getting from this is that most people here don't perceive a real difference between 2007 tf2 and, like, 2010 tf2.
when teams first switched over from quake and ns, things were ugly and muddled, and the really talented tf2 players hadn't yet been sorted out. the first really dominant team emerged in 2008, which was reptile's pandemic, but by like mid 2009 they had been surpassed by carnage's squad (and him and relic hadn't switched over to quake as early as some other players).
by the time you get to 2010, you've had col/loaded with carnage and jaeger and those guys around for a while, blight.fanom with TLR and ruwin shows up, the other blight has harbleu and platinum, and then you get emg with b4nny and yz50 and x6 with kalkin tlr and harb by the end of the year. by 2012 you already have the sick original mixup lineup (pure, enigma, ruwin, tlr, harbleu, platinum). you also have the gunboats, which had started to become more common (though not universal, and not for pockets rly until tri and chess club among a few others). in short, tf2 had changed a LOT in that window.
if we are talking an actual 2007 team, they'd basically just be above-average pub players. by 2010-2012, you have a real team on your hands. would that team beat a modern-day open team? not sure. I think they'd be really good at certain things in comparison (comms and being on the same page, ground rocket aim, scout aim), and significantly worse in others (jumps, movement, demos being used to modern stickies, how much is expected of medics these days). my guess is they could have a shot on granlands ofc, and maaaaybe snake or gully, but would get steamrolled on slightly newer map designs.
I guess if by 'open' you mean newcomers the old team would win, but if we mean the equivalent of esea-open (so like rgl im or main) the latter teams would prolly win.