Like Kevin Feige mentioned, Spider-Man: Far From Home already has Nick Fury, Maria Hill and Happy Hogan serving as representatives from other corners of the MCU, and if the goal is to show Spider-Man triumphing over great adversity, then show him doing so rather than calling for backup. As nice as it would be to see Sam Wilson in a Captain America uniform, that shouldn’t interfere with spotlighting the Web-Slinger properly.
Article source: https://www.cinemablend.com/news/2475668/spider-man-far-from-home-almost-included-an-anthony-mackie-cameo