We are close to halving, and there isn't much time left according to some experts. So if you haven't made any investment in the market till now and are still waiting for a major correction then you should start your DCA from now on until the bull appears in the market. Market rallied after red september but it is nothing compared to what is upcoming. So as you have said whats left will only be regret if you don't take any action right now. That doesn't mean you will go all in at once. Just try to invest gradually to build up a portfolio.
Time is really running out for those that are still on the sidelines and have yet to decide to invest or not, and the longer they wait the higher the price they will have to pay if they finally decide to join this market.
I can understand they may not like to buy after the sudden recovery we have been experimenting, and some of them may like to wait to do this until a correction takes place, but since there is no way to know if the correction will actually come, they need to take a decision and do so soon.