I think most people here are too fast to a conclution. The statement "An agressive strategy is more effective at winning than a passive strategy, because Froyo beat WG" is not sound. Lets say WG executed their passive strategy with a 90% efficiency, and Froyo executed their agressive strategy with 97% efficiency. This can mean that when perfected a passive strategy is better. And the main reason Froyo won is due to that they were better at executing their strategy, not because the strategy it self is better. Froyo is a well established team where multiple members have LAN experience and they have played together for years. Even with the roster mixup they got players who are experienced playing with B4nny and habib. I don't think it is unreasonable to expect Froyo to execute their strategy better than WG.
The idea stated in an earlier post "WG will change their playstyle if they keep loosing" is also a bit questionable in my opinion. In theory it makes sense, however if there is no changes of the value B on a scale from 1 to 10 WG will not lose until next i-series and not change their playstyle. For this to happen WG needs to lose multiple times, losing once a year might not be enough. Between i46 and i49 this happened. We saw the huge ass changes Darn predicted. EU started using gunboats and soldier play started getting more agressive. NA started using quick fix and their playstyle slowed down. I don't think losing i69 will have the same effect on EU tf2 as losing i46 did. I have no idea if WG will think "We lost because we did not execute our gameplan good enough" or "We lost because our gameplan was bad". This will not be an easy question to answer because the dataset is small.
It is really hard to balance the game to make the most effective gameplan the most fun to watch. Maps have to be designed so the team setting up a push can force the defending team to make an opening. However if its to easy its boring. The pushes have to have a success rate high enough for the team to be able to use openings that are given. However the defender also needs to be able to have a successful hold. Failing a push has to be punishing enough for the defendinwever if it isg team to go agressive and gain map control. Ho too punishing teams will wait longer for a better opening before pushing. There are so many elements that have to be balanced. Considering we play a game the developers don't update, and when they do they do not focus on 6vs6, it is hard to make it so that the most effective way to play is the most fun to watch.