The way I see it "entitle" = "in title". People in their title as citizens have a right (often from birth and unalienable) to certain things such as passports.
"Eligible" means you're able to be elected, but you must still be elected. Different from a passport, you may be eligible to a visa, and at some point an officer is likely going to interview you and decide whether to give you one.
People are entitled to a passport but only eligible to a visa. You can assert what you're entitled to, but not what you're eligible to.
> entitlement implies to me that the person has invested some time and resources in asserting their right
That's only when your title was earned, which not all are; some are born into them.
> I believe eligible is defined as meeting some criteria for, not necessarily being chosen though that could be a criteria.
The confusion may have started when decisions became more automated into "criteria" to be checked for by bureaucrats that no longer have the deciding power they once had (and later further automated by software), but "chosen" is in the latin root of the word. For example, "chosen" in Spanish is "elegido", "choosable" would be "elegible". "Eligible" = "electable" = "choosable". They're all basically synonyms.