Also, if you're good enough, it really doesn't make a difference. Unless they shut off all trade
Shutting off all trade is standard practice with my Settlers crowd for anybody who is more than one point ahead. Settlers is much more about strategically managing people's perceptions than it is about strategically managing the board.
Self interested players might be tempted to trade with a leader if they thought there was any benefit in coming in second instead of third, but we play to win. Since trading with a leader who has 6 or more points means you're pretty much guaranteed to lose, we generally don't do it. It makes it pretty tough to run away with it unless you get lucky up front, which basically means we can now predict the winner about 75% of time before the first full turn, as soon as the starting positions are chosen. At that point it becomes less fun. Why bother to play when the whole game is basically decided by how the board deals and what your initial placement order is?
Yup. I stopped playing Settlers a few years ago due to these reasons (well moreso the fact that unless I play with hardcore players like yourself, I nearly always win regardless of board placement and dice rolls.. game doesn't become as fun at that point.) If I had a group like yours though, I'd be in the same situation.
For the OP, and more casual players, it's quite a fun game, IMO.
I'm not a fan of Ticket to Ride due to strategy, but enjoy Dominion as I used to play CCGs, and deck building was my favorite part of that, and Dominion is deck optimization, more or less.
I've heard good things about Puerto Rico and Carcassone, but don't have enough game playing friends locally to do much gaming anymore. My local friends prefer more "party" games like "Apples to Apples" or, at best, Taboo or Cranium. Oh well.