Character creation isn't the *defining* feature of a TTRPG, it's a *nessecary component*. There's a lot in a TTRPG that can be removed, but if you remove *that*, you end up with something else. A board game, an improv game, some kind of really weird storytelling game. It is *nessecary* but not *sufficient*. The other thing I would say that defines the TTRPG is that you are playing a role that is not you, in a setting that is not the one you live in (i.e., the real world), with other people who are all either doing the same thing or coordinating the game and setting (i.e. running the game). So, a TTRPG, then, would be a game where multiple people sit down to create a character that then is role-played in a setting not their own (Middle-earth, the World of Darkness, Faerun, Seattle 2077, etc).
As for what counts, it's pretty broad. A player is creating character when they are making ludo-narrative decisons to create the role they are going to play. If the game has selecting a class, doing 3d6 in order, and then starting the game, you have character creation. You rolled stats, you picked a class, and now you are playing Gandalgrag Ironfist the dwarven warrior. If the game has a set of options you pick from a list, like Apocalypse World or the A:TLA TTRPG, then you have character creation. And if you have character creation, you are on your way to a TTRPG (next part is a setting and a group, but those are the easy parts).
So, if you (for example) get togethet with your friends to play Kobolds Ate My Baby, you are rolling four stats, picking a couple traits, and then using those stats and traits, interacting with a setting with your friends, who are all doing the same thing (or running the game). KAMB is a TTRPG. Talisman is not, it is a board game. You create the role you want to play, then you and your friends play the role.
Oddly, the table-top part of the TTRPG *is* removable, and it *doesn't* make it not a TTRPG, but that's sort of "well, we all live at home on the internet now, thanks assholes in power" thing.