Is it best to wait for the right time to buy or just keep on investing & buying shares with individual stocks? (10-20 year time horizon?)

I feel with index funds or etf’s, there is not as much waiting for the “right time to buy” as much compared with individual stocks. It’s more simple.

But if investors choose to invest only in individual stocks in the hopes for more gains…

Would it be best to just keep buying shares despite the price and ignore the ups & downs of the market? (For long-term investors)