Where do you put modular engine/framework hybrids like Bevy? It owns the game loop so it's technically an engine but you can swap out just about every part of it, even rendering and window management. Tiny Glade only used the core ECS with every other part being custom.

Framework, Bevy is definitely not an engine.

Does it do one thing? It's probably a library.

Is it a collection of libraries that work together focusing on primitives with callbacks? It's probably a framework.

Does it load levels? Have its own schema for an entity? Provide a multiplayer server protocol, and build on primitives? It's probably an engine.

Libraries -> frameworks -> engines -> games.