I think you should always be identifying patterns.
All scales can be broken up into groups of 3 and 4 fingers. Without understanding this critical pattern learning all the scales will seem especially difficult.
- C major and scales starting on white keys using sharps in the key signature G, D, A, E, B in the right hand all use the same finger pattern 123,1234,1.
- F major and scales starting on black keys Bb, Eb, Ab, Db, Gb in the right hand also use a regular permutation of 123,1234,1 like this...
R.H. 1234,123,1234,123,1234,123,1234
------------------------------------
---F:1234,123,1---------------------
-----Bb:4,123,1234------------------
---------Eb:3,1234,123--------------
-------------Ab:34,123,123----------
-----------------Db:23,1234,12------
---------------------Gb:234,123,12--
------------------------------------
Another way to understand the pattern of fingering for the 'flat' keys is start with the right hand fingering for C major 123,1234,1. Keep your hand in this "C" position and then add the flats for the 'flat' keys. First add the Bb then Eb, Ab, Db, Gb, Cb. As you add the flats maintain the fingering 123,1234,1. This fingering then covers all the standard fingerings for flat keys.
R.H. 1 2 3 1 2 3 4 1
F : C D E [F] G A Bb C
Bb : C D Eb F G A [Bb] C
Eb : C D [Eb] F G Ab Bb C
Ab : C Db Eb F G [Ab] Bb C
Db : C [Db] Eb F Gb Ab Bb C
Gb : Cb Db Eb F [Gb] Ab Bb Cb
* tonic for each scale is given in brackets
- similar patterns are found in the left hand.
- except for a few exceptions the fingerings do not change between major and the various minor scales.
Some methods explain these patterns, like this one...
...but IMO too many don't show crucial patterns and just notate endless scales.
If we return to part of your original question...
...learn each [scale] as a separate piece of knowledge... [or] memorize the patterns?
...it seems clear the scales are not separate and unrelated, but rather follow patterns. It's counterproductive to not seek out these patterns.
There are other patterns regarding the position of the black and white keys. Things like major 2nds and major 3rds will be keys of the same color except when crossing the B,C and E,F half steps. Perfect 4th and 5th are always the same color keys except when the the combination B and F.
Regarding memorization, I'm not sure if that's the best word. It may suggest too much conscience thought. Awareness of patterns and development of reflexive motion is maybe a better way to think about it.
Whichever way you think about it recognizing patterns should not be twisted to mean something like you do not need to practice all the scales. That would be wrong. Despite the repeating patterns the specific, physical "shape" of each scale is unique. The fingers and wrist make small adjustments to reach the changing key positions. They should all be practiced.