The meaning of greed varies from merchant to merchant. I agree with your opinion that when the target has been reached, traders should immediately take profit rather than expecting a bigger profit. It was greed, of course because they had set a target. So obviously they have to be very consistent with their strategy and have to exit when the targets are met.
But when it comes to holders then I don't think they deserve to be called greedy especially long term holders. They need not give up on the plan if they still see a greater potential for more returns in the long term.
Considering the price went from 15k to 30k+, we could consider that greed could be a good think. If you bought at 15k and sold at 20k not to be greedy, you would have lost a 50% increase, if you sold at 25k, still same, hell even if you sold at 30k, there was another thousand dollars increase that you missed and maybe it will keep on growing more in the future? I believe that we shouldn't really consider this as a big deal, it is not really as big of a deal as you think it is.
I believe that we are at a stage where greed is good because the price might go a lot higher. There are a lot of people who end up with a return that will take some time and with halving around the corner we could go into big bull run, so keeping your coins and not selling them is still a smart choice.