@TrixieRuby possibly more HIIT workouts? Skiing is not a sustained slow cardio sport. It is made up more of intense bursts for a few minutes, that demand strength, cardio, speed, and balance. If one of those categories is undeveloped I find that I work harder than I need to.
Even classes vary so much. Age is a factor but I am regularly outrun and outlifted by women 20 years my seniors. I do have the speed and the balance.
Not sure where and how you train but seeing if you can add speed and balance exercises may help. I find that easy trail hiking and road biking are great for cardio but lacking in the foot and eye speed coordination.
The one word of major caution though, is to not get hurt while training for the winter season.