I think you've approached this from the wrong angle (pardon the pun).
There are takedowns that work with the attacker and defender squared up - look at something like tomoe-nage. Not every attack in Judo is done with angles.
I also don't agree that we only apply power in straight lines - in fact a lot of the power we are able to generate is rotational, and a lot of throws require this rotation.
In Judo we have the concept of Kuzushi, which means off balancing - as long as you are able to off-balance an opponent, you can open them up for an attack - but this doesn't necessarily mean an 'angle' if even often it can be. I great example is a simple change in direction of forward throw to rear throw (or vice versa)