As a HC player (Barbarian) who is currently sitting at #41 on the leaderboard with GR73 (Around #700~ on the SC ladder), I have to disagree with the fact that it isn't a challenge.
We just generally take it slower on the ladder while pushing. Usually we aim for GR70 to enable Primals and then we focus purely on farming and getting our gems up than pushing the ladder. Unlike SC, we can't afford to run into a high grift un-prepared, we have to make sure we 'feel' ready to take on the higher grifts, to know our limits, to know which gfrift mobs we can realistically take on. There are countless things that HC players must do before pushing the leaderboards and that is our 'challenge' and the reason we play hardcore.
By no means is hardcore challenging in the first 30 days of a season, there is no challenge when building up a set and hitting GR70 in the first few days, that is 'basic' stuff. The challenge comes when you have the balls to push rifts that you literally have to proc 2-3 times to even get through and come out the other side victorious.