Why does a saddle have to be level?
Basic comfort I suppose. You might well feel comfortable as it is as you've not had it any other way, but simply straightening it might make you go WOW, so this is how it should feel.
Have a look at
THIS site about bike fit, it might be useful, it might not, but it certainly won't do any harm.
IMO the general rule is most folk are fine with a dead straight saddle, and in any case it's the best recommended place to start with fitting.
You might need some slight adjustment tweaks from straight, but chances are straight will be right.
FWIW I used to have my saddles like these two pics, and yes they were both my actual bikes and my actual saddle angles. The Trek in particular makes me feel
now whenever I see this pic
and these are my current bikes, note the difference a few years and a little knowledge makes