I’m sorry but Captain America wouldn’t have been a better mentor for Peter in the MCU. Sure- I agree that Peter would have been more torn about the Accords if he had all the information, but Peter’s whole thing is “responsibility over personal self”.
Spider-Man has always been a character riddled with the guilt of a death he could have prevented, and spends his entire life trying to rectify that choice- feeling responsible for the well-being of others. This is reflected in almost every version of Spider-Man, and is shown in his first ever appearance in the MCU:
“When you can do the things that I can, but you don't, and then the bad things happen? They happen because of you.”
Tony’s entire motivation with the accords is responsibility, and Peter’s guilt is directly mirrored with Tony’s- something we see at the start of civil war with that women blaming him for her child’s death. Tony needs to fix- needs to protect, and to him- as flawed as it may be, the accords are a way to do that.
So here we have Peter Parker- a tech genius who creates web shooters out of scraps and was given insane powers at 14 and used them for good instead of becoming popular. He’s a snarky kid whose impulsive and wants to do good so god damn bad but keeps messing up, keeps hurting the ones he loves and becomes too obsessed with a suit that makes him feel invincible.
You’re telling me the best mentor for this kid is Captain America- just because they both are New Yorkers who were given powers? Their motivations are entirely different- and the way they go about doing things don’t match up.
Tony and Peter come from completely different backgrounds, and on the surface level- are different people. When you look at the core of who they are, how they act- why they do the things they do- Tony is the person who can understand Peter in a way the Steve would never be able to.
People like to criticize MCU Peter for being “Iron Man Jr.”- but he isn’t, not at all. He’s not a sidekick, not dependent- the whole point of Homecoming is that Peter doesn’t need Tony’s tech to succeed, nor his permission to be a super hero. Far From Home worked to show us that Peter would never be the next Iron Man- because Iron Man is his own thing, and Peter is Spider-Man- a hero in his own right. Peter is the Legacy- not a copy, and not Iron Man’s legacy, but Tony Stark himself. The most telling and raw way to show that as a concept, and it was sitting right in front of us.