Not all AA are the same. The vaseline smear you complain about is just Temporal AA. See https://www.reddit.com/r/FuckTAA for more info.
Not all game engines need to use TAA, and usually is just because the devs were cutting corners.
Edit: even the post mentions it, https://blog.frost.kiwi/analytical-anti-aliasing/#clarity-should-not-be-a-luxury
Wonderful blog with embedded WebGL examples. Kudos!