Ooh, funny - though the strawmen are strong here:
1. Lineup doesn't matter - nobody said that, but that the differences are small, and from a player psychology perspective, some guys care and some don't - and you try to accomodate the former and hopefully have enough of the latter to make it possible. Getting the right players on the field trumps exactly where they hit. You don't want Betts batting 9th, but within reason it's not a big deal.
2. Home field doesn't matter - It does help, but historically it has not been some sort of iron lock the way it is in the NBA. (or the NFL if they did best of 7s) Occasionally you get a team to sweep home games in the postseason (like the 2004 Red Sox), but it is extremely rare. Instead, teams win some, teams lose some. We know World Series teams have won exactly half of the Game 7s since 1946. Home teams lost the first five games of the 1996 World Series and went 1-4 in the 1986 World Series. What sucks is that this is baseball - good teams have 2-3 or 0-3 stretches all the time, usually against weaker competition than the playoffs. You build a team for the ballpark - but even then the results are still not much more than 6 out of 10, which is awesome, but can be scuttled in a short series very easily. After all, Toronto cut through a home field disadvantage with almost no difficulty.
3. Managers matter - and using the bullpen is the one tactical thing which does have value. At the same time, the players still have to perform. But in general, most of a manager's work does not happen during those 2.5 to 3.5 (or in the case of Sox-Yankees, 5.5) hours they are sitting in the dugout.