Alright, let's see your points.
- Start beside Shaka/Atilla
Yeah see, that goes for all civs. And even then, Science civs can more easily maintain their science then other victims of early warmongers can. Oh, and Korea/Babs/Maya need no stinkin' GL to rush ahead in science. In fact, on higher difficulties it usually gets ignored because the AI is too fast anyway. Furthermore, Korea has come medieval a pretty impressive attack-slayer-unit in its arsenal, which helps a lot.
- Mayans
Even with only 3 cities, if you get those cities early, that's still 6 beakers pre-modifiers from various other buildings. The Mayans have science as A bonus, not THE bonus. They're also fast to religion and can get an early great scientist for an additional 8 beakers.
- Babylon
Sure, Sweden can surpass Babylon's range, but on normal maps, that isn't easy. Furthermore, Babylon needs no work to get those Scientists. Also, they have that very early game Scientist, which is an immediate 8 beakers, which at that point is huge. Sweden will not, ignoring world wonders with Scientist points, get that Scientist ball rolling until they reach Education.
Interestingly enough, Babylon and the Maya both have great tools to fend off early warmongers too. Babylon has better walls and a stronger archer, while the Maya can ignore Archery.
Poland, in human hands, is bonkers. Those policies allow them to pull mix-and-match strategies where other civs have to focus. Want a religion-heavy City State game? Poland can fill out both Piety and Patronage with ease. Need more gold instead? Slowly fill in Commerce while blazing through the policy tree.
It's all about being in the hands of humans. Those 4 civs are the best for a good reason in human hands.