The first time I tried getting into competitive TF2, the gunboats were banned and I thought that was dumb so I didn't get into competitive TF2.
Four or five years later I started playing on a competitive-oriented pub server very consistently, and after 250 games of matchmaking in the beta I knew I wanted to play 6s, so I formed an esea-open team.
edit: my first MM game in the first stress test was on everyone's favorite competitive TF2 map, ctf_doublecross.