Starlink directly competes with wired internet. It also competes directly with cell towers in the fixed wireless business and in mobile service for vehicles. Next year Starlink will be competing for mobile service direct to handsets too. Sure, people will use more bandwidth when they get Starlink, because Starlink provides more bandwidth. But that won't increase demand for Starlink's competitors, all it means is people get better service. I find the idea that Starlink doesn't reduce demand for its direct competitors extremely implausible.
Just like 5G could potentially reduce the overall consumption, before we realize that actually we use it to the point where it increases them.
Or just like any other technology, after all.