Experience is the knowledge or mastery of a subject gained through involvement in or exposure to it, generally referring to know-how rather than know-what; i.e. on-the-job learning opposed to book, class, learning.
Experience relates specific activity; aviation, flying, particularly context. That which a person is expected to be exposed to and how to react. This depends on role, task, and situation; and that any future need is a judgement - a forecast of the level of interaction in role, task, and situation.
Flying hours alone do not constitute experience, it’s the content of those hours and retention of that knowledge and skill, and transference of these across types and operations which are important. Also, a mindset never to stop learning.
The opening views in the thread is blatant hindsight bias. Similarly discussion of individual accidents, which can only conclude that the level of experience, or its application was insufficient for that particular situation.
Focus on individuals is again in hindsight, fundamental attribution error, unwarranted blame.
These views should not be used as a basis of training and levels of experience; pilots rarely encounter the same accident, situations do not repeat exactly. Thus the greater need is for experience in judging different situations, the unusual, not trained for events, and have flexibly in acting. Modern experience is more associated with agility of thought, awareness, opposed to physical skills.
Current levels of experience differ from previous; the issue is not that future operations will require same level, content, or quality, but that the combined crew experience should be sufficient for the situations crew’s are expected to manage.
Forecasting future challenges is difficult, Generic experience and skills could help. However it may be easier to limit the extreme situations that crews could encounter, with technical and operational improvements; and not to expect too much from the human contribution in an increasingly complex world.