I have what's probably the most pragmatic view in regards to presets and that is:
If you try a preset and like it, and cannot hear and tell what's wrong w/ it, it means that you probably won't be able to dial in a better/proper setting from scratch at this time.
Or you've just hit the one in a Godzillion time where a preset actually work as is.
So if you load a preset and think that it makes your sound better, you may want to see that as an opportunity to grab a little bit of knowledge.
For example, if it's an EQ, try and listen to what it does exactly - scoop the mids? boost the low end or the hi frequencies? What does it do to your sound and how could you make it even better?
I say if you hit a preset that sounds pleasing to you, by all mean, go ahead and mess w/ it, dissect it, study what it does, try to duplicate it and improve it.
A few months from now, you will probably find that you didn't push it in the right direction, that you overdid this or that. But that's all good. Identifying mistakes is part of the process. Learning often works backwards.