Lessons to learn for the noobs: Never panic sell, never margin trade, you can FOMO if you are here for the long term (5 to 10 years) since it doesn't matter if you bought at $20k or at $5k as BTC will be worth millions eventually.
Given the price didn't dip below 6k across the major exchanges I'd be surprised if many people sold out at below 6k! Aside of that the points are great and hopefully this will be a learning curve for anyone who re-enters the market. For me it was the first time going through such a large dip but I stayed true to what I'd always thought and been told and held through it. Of course there's still a long way to go to recover but breaking 10k is a great start. If the guys who re-enter can learn from their mistakes then the market can only grow stronger in the future.
Like you said, I always believe that newbies are always the panic sellers and most people who have been in this trend for a while and see how things turn out at the end, usually get to see how things end up turning out and then strengthens their future decision when market turn down.