This post is from 2020 when all air travel ceased. It would be nice to see an update with the new creative airline miles schemes.
As for the new miles schemes: airlines used to publish charts showing you earned for X points per mile. The shorthand "miles" referring to FF points is telling. Now airlines use "Dynamic award pricing". It's impossible to tell in advance how much your points are worth.
https://thriftytraveler.com/guides/points/points-principles-...
That trend started in 2019, but it took off as the pandemic wound down.