If we compare the price of Bitcoin has reached this year after it reached ATH, it can be called a good time to buy. Because current price is down 50% from ATH. But it depends on your own decision, as no one can be sure this is the best price to buy. No one can predict what the market will be like. It's all a prediction.
It's always a good time to invest if we're planning it to hold for a long time. If we're aiming for a quick profit, the price right now is quite high, there must be some correction before the price going back to the top again. So it depends on the investment timeline that the investors decide at the start.