If this is tiring, there's zillions of other board games that are alike in theming, complexity, analysis, game length, etc., but have the players compete in parallel most of the time with less opportunities to directly interfere.
If this is tiring, there's zillions of other board games that are alike in theming, complexity, analysis, game length, etc., but have the players compete in parallel most of the time with less opportunities to directly interfere. Don't "fix" Settlers. The problem is fixed by diversifying the games you play.