OP, what you have said is more to be looked into. Old strategies are ok to use but you know as time goes on, new development and technology emanate which calls for upgrade. You upgrading means you discovering new more strategy but however discovering new strategy does not mean you neglecting your old one you can combine both then apply it to a trade which seems difficult for you or you use the knowledge gained from that old trading to make your way through the complexity of any trade you find yourself in.
The idea of studying a market trend is very much important as well as stated by a member while commenting on this topic that would give you a guideline on how to enter the market and also know the exact trading technique you will implore to scale through in that trade.
So In essence, no trading knowledge or idea is a waste. You can combine them in achieving a positive result while trading.
I think having better technology and better understanding of the market thanks to more detailed research, allows us to have a better trading strategies as well. However, something as old as "buy low, sell high" could still work as well.
You may not know when it will be at the bottom, or you won't know what is the top, but you would know something is down when you see it go from 68k to 16k, there is no reason not to buy it there, it's the ideal "buy low" situation. And same goes for when it is 100k in the next cycle, maybe it will go higher, but you just made more than x5 return, isn't that a reason to be happy about? Of course it is, and that's all we need in the end.