(This is my first question here and I apologize and can edit if it's out of place or formed improperly or has other issues.)
The September 20, 2020 news of phosphine found in the clouds on Venus has generated a large amount of cautious excitement from the scientific community. In general the discovery finds a statistically significant amount of phosphine (PH3) in the upper atmosphere of Venus, that cannot be explained with abiotic chemical pathways that are known to occur on Venus. A tentative suggestion is that there may be a biological pathway within the clouds of Venus that creates the amount of phosphine observed. Thus, the hypothesis is that Venusian "life" may be responsible for the creation of phosphine. Accordingly, there is an unexplained phenomenon and there is a suggestion that it is reasonable to have an appeal to alien life to explain the observed phenomenon.
The 1968 book Chariots of the Gods? does not explain how ancient civilizations created megaprojects and instead hypothesizes that aliens could be responsible for some ancient megaprojects (such as the Nazca lines/Egyptian pyramids/etc.) Accordingly there is an "unexplained" phenomenon and there is an appeal to alien life to explain the observed phenomenon.
I find it easy to dismiss Chariots of the Gods as pseudoscientific claptrap, not least because the assumption that ancient civilizations were incapable of owning their own history and artifacts marginally racist and bordering on repulsive.
I also find it easy to dismiss the book because the appeal to aliens as gods seems like a replacement of one curiosity (how could ancient civilizations build all their megaprojects?) with another, harder to disprove hypothesis (could be aliens!) However why does that second dismissal not carry over to phosphine on Venus? "How could there be phosphine on Venus? Could be aliens!"
Why do I feel more comfortable pondering whether there is a biological pathway for the creation of phosphine on Venus than wondering about ancient aliens building Mayan temples?