You can memorise all the modes, triads, scales etc without practical playing application. What's most important is understanding how the note you want to play relates to the key. If you want a b9 sound over that chord, do you know which note to hit? Or in your head are you thinking and struggling which position to press? Most people are in the latter category because their rely on their eyes more than their ears when it comes to playing. They SEE shapes, they don't HEAR shapes and that's why they can't apply what they have 'memorised'.
Using stuff 'out of the box' is a good thing but only if its intended and not by 'accident'. Imagine this, you go to the spice rack, grab a random number of spices to season a steak. Tastes great? Well its an accident because the result was unintended. Same thing for any art, the intention behind the choice is everything. That's where true understanding takes place. No need to explain theoretically, but understand the sound in relation the current key. How? Many ear training methods nowadays which you can use. Just do a search.