I think that “good enough” needs to be defined by the use to which vernacular names are put by iNat users. From the perspective of a new iNat user with an interest in biodiversity but no formal education in biology, vernacular/common names are of more importance than formal taxonomy. I’m pretty sure that the typical middle school kid assigned to a bioblitz will be starting with common names and it’s how they will navigate the site until they get to the point that scientific names matter/make sense.
I have degrees in biology that focus on fish and aquatic/marine life and I have some experience with other taxa, so I often use scientific names when I’m working with those familiar taxa. On iNat I’m mostly learning about other things (I have one fish observation) so I do a lot of searching with vernacular names. I’m occasionally surprised that things don’t pop up when I use a name that turns out to be an older, regional or otherwise unfashionable moniker.
I think it’s important that the common names filed on the observations reflect to the greatest possible extent the way new folks will refer to the stuff they observe. That means regional variation needs to be reflected and it means that vernacular names cannot be unique to single taxa on iNat, a position that I think contradicts the established practice but which is how the world is actually configured. If that causes some confusion it’s because the world is a confusing place. A disambiguation function can deal with conflicts. The practice which aids users to learn with the fewest hurdles should be the default, wherever possible.
The discussion in the topic posted by @liamragan regarding importing indigenous names is also something that should be considered. In the case where there is an indigenous name for a taxon and no other accepted common name the indigenous name should be the default common name. It works fine for moose.
I agree that inventing names is not something iNat should do.