I don't think either of these are too abstract, and both have concrete mechanics that integrate them into the game.
Population is mechanically grounded by food, housing, and amenities. All else equal, is it more important to ramp up your production (or science or faith etc) or keep your cities growing by securing amenities and building adequate housing? That's not an abstract question.
Territory is the turf you're sitting on. Is it more important to secure more cities and tiles or to spend your food and production on other things? How important are specific plots of land? Worth securing vs other priorities like building traders or districts? This is especially relevant with districts, which completely remove the tile's base yield from the game. Especially mid-late game, you're definitely going to have to figure out how to balance development with workable tiles in your cities. That said, if you have more territory, that's less of an issue – and that's a big reason why you might build a settler before a campus or buy a couple key tiles before upgrading your units.