I love Kart games and simply found that my play-style preference I suppose. You're right though having levelled up characters should help. My characters were all newbs 1st time round, and I hadn't 'cheated' yet with a spark farmer. I always struggled with the 'Collect the orbs within the time limit' games for some reason. Having my characters super-jump unlocked should now help no end.
I found the repetitiveness of Toybox in the HERO DESTROYER machine, the level that unlocks all the different sidekicks through repeated grinding. I spent so much time farming and levelling up! if I have a regret it was having done that for so long. As now to lose all that progress in the console UPGRADE feels like wasted hours.