> modes required modifying certain notes from a major scale
But why though?
If you're improvising on a dominant (e.g. a G7 in the key of C Major) with a G Mixolydian scale, you're actually not playing a Mixolydian sound, but Ionian, since your tonal center is C Ionian. It is true, it is indeed a G Mixolydian scale and it is using the tonal contents of our key C Ionian. But our frame is Ionian, so what is the purpose of adding Mixolydian other than ease of construction of the scale?
But why though? If you're improvising on a dominant (e.g. a G7 in the key of C Major) with a G Mixolydian scale, you're actually not playing a Mixolydian sound, but Ionian, since your tonal center is C Ionian. It is true, it is indeed a G Mixolydian scale and it is using the tonal contents of our key C Ionian. But our frame is Ionian, so what is the purpose of adding Mixolydian other than ease of construction of the scale?