A long time ago, in a far away land, I used to race cyclocross competitively–aka, I trained for it and actually tried to do well.
After being yelled at for being a sandbagger on multiple occasions while racing in the B category, I upgraded to A’s, which meant not only was I racing with the best amateurs, I also raced with any pros who showed up. As anyone who has gone from B to A knows, it’s a huge leap. You can’t fumble through the race relying on either technical skills or fitness alone. You have to have both.