Mistakes can be made by everyone and we all can learn from our mistakes, big or small, but it's very painful if mistakes will be paid by own money or most of capital we have. It's preventable if people are ready to learn and have good preparation for their investment.
Without mistakes we never learn to develop towards new things, but a solution is needed after making an initial mistake in investing so that people can understand the positive and negative impacts much better. Learning will provide preparation for all possibilities and in that way we will be much more prepared.
Yeah, mistakes can be made, and they should be learned upon afterward.
It's wiser and better to learn from the mistakes of others (regarding what was discussed there about CEXes and such), but the best teacher is your own experience of a mistake made.