That's not actually a good thing. Most "soft AH" (the classic Axis/Confederate victory story) just uses the alternate history as the basis for what's to happen. So criticizing it on plausibility grounds, while valid, is kind of like criticizing Star Wars for having spacecraft behave like WWII fighters and laser swords being viable. (The reverse is also true, to be fair: Axis victories and the TL format do not go well together).
Really, the TL format is only suited IMO for a certain type of alternate history involving a lot of worldbuilding and explanation that can sustain the readers interest on its own. 95-99% of published AH doesn't fit that category.
And Star Wars
, like all other advanced tech/FTL is very much Writer's Forum or ASB.
The biggest issue with most published AH is that it, quite sensibly, is aimed at a much broader reader base than that which is present on the Board. It is almost all proper fiction (i.e. Writer's Forum or depending on the elements ASB). As an example - There is a story (by Turtledove? Been half of forever since I read it) that features a British action that bring the Union and Confederacy to end the Civil War and go after the British. It goes into great detail about how the Union monitors manhandle the HMS Warrior
. Reads great, quite fun overall, with Longstreet and Sherman working side by side, etc.
Problem is that the description of Warrior's
design is hot garbage, Put that in pre-1900 and the legions of Royal Navy experts (a term not used in any negative way, some of these folks could write books on the subject of the pre-steel RN) would have stopped the thread dead by utterly dismantling the critical plot element that allows the union ironclads to destroy Warrior.
The average reader wouldn't care, hell probably never even heard of HMS Warrior
until they read the book.
Successful book, DOA in pre-1900 (but likely as not a major hit in Writer's).