Instagram Control + Z the IGTV button from the application.

Is this an indictor IGTV is faltering?

With only seven million installs of IGTV in 18-months, it's a drop in the over billion IG users.

Most users are consuming IGTV from their regular IG feed.

So why is it stagnating?

Likely because long-form videos are expensive to make, and there's no transparent revenue model for publishers to jump on board.