Is dollar cost averaging a reliable form of long-term investing? Can a more experienced investor benefit from it as well?

Absolutely. When you DCA, you're taking away the guesswork of figuring out when to enter the market.

The idea here is that equities over time will have a very high probability to provide you with positive return. So just remain invested.

But there will be times where you should also top up your investments. After a recession, you should put down a lump sum, and increase your DCA amount until the market rebounds.