The short version without going into details:
Case 1: After Effects output H264(.mp4) = Bad
Case 2: After Effects output .avi/.mov + feed into Adobe Media Encoder to output H264(.mp4) = Good
Problems Tackled!: Adobe After Effects H264 Output Pixelated/Blurry
The short version without going into details:
Case 1: After Effects output H264(.mp4) = Bad
Case 2: After Effects output .avi/.mov + feed into Adobe Media Encoder to output H264(.mp4) = Good