Alternate histories that are useless ideological wankery;
There are a very few alternate history points of divergence that literally need intervention by God or a sufficiently-minded alien from the Q Continuum to bring them about. Sure, anything is possible but for some things improbability is far too overwhelming to make a decent story about them.
The first of these is a Nazi invasion of England via Operation Sealion. The Germans had no way in Hell to pull that off, they had no navy, their air force was not designed for that purpose, and the British were rather more formidable than the Germans realized. Sealion is as mythical as a polka-dotted unicorn drinking from Russell's Teapot.
The second of these is the Confederacy winning the US Civil War. It has a very, very narrow timeframe to do that in if we're assuming a recognizable scenario. Once the Confederacy resorts to conscription the South will weaken every year no matter how well its armies do on the battlefield, while Northern strength is ever-increasing by comparison. Any long war scenario and the only question is when and how the Union defeats the Confederacy. For that matter the South could only win the war in the East but it lost it in the West due to the Union's three best generals being up against the Confederate General Failures.
Another irritating thing one sees in alternate history are borders that are the same as our world's without sufficient logic. Kazakhstan, and a unified India and China are obvious examples. For that matter a unified China including Tibet and Xinjiang is another obvious example. Then there's that the potentiality of a late Medieval Chinese industrial state is always overlooked in favor of steampunk Victoriana, with the problem that an industrial China's a lot more interesting because Britain was two tiny islands. A unified and industrialized Chinese Empire would be a juggernaut on the US scale.
On the other side of things, Japan *always* ends up being the only non-Western power to industrialize and overtakes China in the process despite that Japan was traditionally a backwards backwater of the Chinese dynasties. This is no doubt due to ignorance and people being unwilling or unable to spin a tale about super-Korea or super-*Vietnam. Then there's the question about why nobody ever postulates worlds where William Henry Harrison never attacks Prophetstown which makes the War of 1812 very interesting.
The other major vexation in alternate history series is a tendency to uber-wank societies like the Confederacy and the Nazis. Timeline-191, despite being one of the lengthiest timelines gets really, really ridiculous. Not only does the Confederacy get a handwaved emancipation but it lasts too long in World War I and ends up with both an atomic bomb and the ability to run World War II and a Holocaust analogue at the same time, which would be rather beyond anything realistic. And the tendency for Man in the High Castle-type timelines where the Nazis end up more like Sauron than they do a society more inefficient than Stalinism that burned out in 12 years is both annoying and has a lot of unfortunate implications. The ones with the Confederacy do, too, but then the Confederacy and its crimes are regularly overlooked by of all parties the party of Lincoln and Grant so WTF do I know.
Then there's the converse tendency where some societies are *never* allowed to go anywhere. The most egregious example is the Ottoman Empire where points of divergence include things like a successful Treaty of Sevres (*shudder*) or the Greeks taking over successfully the parts of Ottoman Anatolia where most Turks lived, leaving aside that in real life they showed that had they done so Turks would be as numerous as Cherokees today. Or alternately one never sees Amerindians having their own version of a Meiji Restoration despite the length of things like the Auracao War or the Zapatista Revolt. Nor does one see Soviet-wanks the way one sees Nazi-wanks even though logically the one should be more plausible than the other (given the USSR lasted into the 1990s where Nazi Germany lasted barely over a decade).
The first of these is a Nazi invasion of England via Operation Sealion. The Germans had no way in Hell to pull that off, they had no navy, their air force was not designed for that purpose, and the British were rather more formidable than the Germans realized. Sealion is as mythical as a polka-dotted unicorn drinking from Russell's Teapot.
The second of these is the Confederacy winning the US Civil War. It has a very, very narrow timeframe to do that in if we're assuming a recognizable scenario. Once the Confederacy resorts to conscription the South will weaken every year no matter how well its armies do on the battlefield, while Northern strength is ever-increasing by comparison. Any long war scenario and the only question is when and how the Union defeats the Confederacy. For that matter the South could only win the war in the East but it lost it in the West due to the Union's three best generals being up against the Confederate General Failures.
Another irritating thing one sees in alternate history are borders that are the same as our world's without sufficient logic. Kazakhstan, and a unified India and China are obvious examples. For that matter a unified China including Tibet and Xinjiang is another obvious example. Then there's that the potentiality of a late Medieval Chinese industrial state is always overlooked in favor of steampunk Victoriana, with the problem that an industrial China's a lot more interesting because Britain was two tiny islands. A unified and industrialized Chinese Empire would be a juggernaut on the US scale.
On the other side of things, Japan *always* ends up being the only non-Western power to industrialize and overtakes China in the process despite that Japan was traditionally a backwards backwater of the Chinese dynasties. This is no doubt due to ignorance and people being unwilling or unable to spin a tale about super-Korea or super-*Vietnam. Then there's the question about why nobody ever postulates worlds where William Henry Harrison never attacks Prophetstown which makes the War of 1812 very interesting.
The other major vexation in alternate history series is a tendency to uber-wank societies like the Confederacy and the Nazis. Timeline-191, despite being one of the lengthiest timelines gets really, really ridiculous. Not only does the Confederacy get a handwaved emancipation but it lasts too long in World War I and ends up with both an atomic bomb and the ability to run World War II and a Holocaust analogue at the same time, which would be rather beyond anything realistic. And the tendency for Man in the High Castle-type timelines where the Nazis end up more like Sauron than they do a society more inefficient than Stalinism that burned out in 12 years is both annoying and has a lot of unfortunate implications. The ones with the Confederacy do, too, but then the Confederacy and its crimes are regularly overlooked by of all parties the party of Lincoln and Grant so WTF do I know.
Then there's the converse tendency where some societies are *never* allowed to go anywhere. The most egregious example is the Ottoman Empire where points of divergence include things like a successful Treaty of Sevres (*shudder*) or the Greeks taking over successfully the parts of Ottoman Anatolia where most Turks lived, leaving aside that in real life they showed that had they done so Turks would be as numerous as Cherokees today. Or alternately one never sees Amerindians having their own version of a Meiji Restoration despite the length of things like the Auracao War or the Zapatista Revolt. Nor does one see Soviet-wanks the way one sees Nazi-wanks even though logically the one should be more plausible than the other (given the USSR lasted into the 1990s where Nazi Germany lasted barely over a decade).