Your best finish may be 477th, but there are a few thousand entrants in most of those tournaments. You're generally right in the middle of your tier. Being competitive is not determined by your chances of winning, rather, it's where you place versus the rest of your peers.
In all tiers there will always be a spread from top to bottom. No matter where the numbers fall there will always be players who have a tough time competing and may finish near the bottom more often than they'd like. But, if we were to drop all of those players from the pro tier into the Amateur tier then you have a whole new group of players finishing at the bottom of the Amateur Tier. It's cyclical, so we have to draw a line somewhere.
You were promoted to Pro because at some point you exhibited the ability over your best 10 of your last 14 rounds to get below the score requirement, so you demonstrated the ability to compete in the Pro tier by doing that.
More tiers will released in the future to help narrow down the gap between the top and bottom levels, but no matter how many tiers there are and no matter what the numbers are there will always be folks who struggle near the bottom of that tier.