You can rent access to nearly real-time custom satellite targeting for <$3k per image. That means while you're correct that not all countries can afford it, most can.

I admit I'm incredibly naive on this subject, but what makes it so hard to track an object as large as an aircraft carrier when starting from a known position such as a naval port?

Those are the few countries that France needs to worry about.

Doesn't matter whether Estonia, Honduras, Laos, and Luxembourg can track their carrier, or not.

EDIT: In confined waters (like the Mediterranean), many more countries could track the carrier if they cared to. Even back in the 1950's, the Soviets got quite adept at loading "fishing boats" with electronic equipment, then trailing behind US Navy carrier groups.

was

Billy Boy from the Island can use commercial satellites to map mud huts for his vaccine NGO, i'm sure any nation state can find a few quid to locate a war ship.