No years of service under various Captains as he worked his way up the latter, we know that Earth possessed other starships prior to the construction of the NX-01. We never heard even a vague reference to Archer serving in any capacity on any of them. No stories (Archer loved telling stories) of Archer previous Captains, prior ships. Archer - by canon - was never a section chief, never a first officer, never had a ship's commander as a mentor, never had a crew under his leadership. Test pilots do not have "crews."
That's not true. In
Minefield, Archer talks about a CO who had a different philosophy ("they're your crew, not your friends") than he did as he explained to Reed how he was trying to develop his command style. Clearly there's more to Archer's backstory than what we saw in
First Flight.
Zero interstellar adventures and mishaps
..., before assuming command of the NX-01, Archer apparently had never left the solar system.
I don't recall there being any statement one way or the other on this point.
I agree with
HR; Archer was (ideally) meant to be inexperienced, representing humans entering the wider galaxy with our usual naive bravado. He was inconsistently written. But I think the charm of the character was his ability to creatively work through problems. He didn't have the backup or training or even the policies of Kirk, etc., so he just used whatever was in his toolbox and figured it out as he went along. Which made his evolution into the guy who lays the foundation for the Federation so interesting and satisfying to me. He literally goes from distrusting and disliking Vulcans (
Broken Bow) to being the only person BOTH Vulcans and Andorians will trust to mediate peace talks (
Cease Fire) to the cord that binds Vulcans, Andorians, and Tellerites, all of whom loathe each other, together (
United).
He saved the world.
He didn't lose a crewmember until well into the Xindi mission (three years in).
He is the only Enterprise captain whose ship wasn't destroyed.
His dedication and compassion made the Organians change their minds and rethink their test.
Of all of the captains, Archer is my favorite, precisely because he is flawed and human and capable of growth.