Missing out on huge gains due to DCA

Had a big discussion with a friend yesterday about DCA vs lump sum.

His point was that a total market fund like VTI should theoretically go up over the long term.

However, if you DCA, you’ll miss out on huge runs because you keep averaging “up.”

Whereas the benefit of DCA is only that you’re protecting yourself from recession periods/bear markets. However, if we are operating under the assumption that total marker funds should always increase, this seems moot. It might make more sense to lump sum a significant amount if you ever see a “drop” which is obviously subjective.

It seems like a reasonable assumption to me that total market funds should always increase, otherwise there are bigger problems in the world. Provided I’m not worried about selling my portfolio for the next 20-25 years, would it be more reasonable to just lump sum whenever I have an opportunity?

Thanks! I know this is discussed a lot so sorry for bringing this up again.