11.30Don't change scale mentally on every chord yet

You could think:

Dm7 = D Dorian

G7 = G Mixolydian

Cmaj7 = C Ionian

But notice:

all three use the same notes:

C D E F G A B

because this ii–V–I is diatonic to C major.

So for now, simply use:

C major scale

while targeting the chord tones of each chord.

This is much easier and more musical.