No. It is not too late because there are many people who uses bitcoin who wanted also to invest but they have a question in their mind if it's too late. It's not yet too late because as long as bitcoin never stops, investment will never stop also. As long as there are users, there is bitcoin and if there's bitcoin, there will be an investment.
I agree with you, it is not too late to invest and be part of bitcoin but for now you should wait for the right time to invest to bitcoin because it can be you lost if you invest in the wrong time.
Yes, we need to know when to invest and when to sell so that we can be able to avoid huge loss in our investments. New investors must study and search more so they can avoid losing more funds in their investments.