Your focus isn’t broken. It’s been trained by apps for years. It can be retrained.

Attention is a habit rather than a fixed trait, and yours has had years of practice at short bursts with a reward at the end of each one. That is training, and it worked. Long tasks feel impossible not because something is damaged but because you are out of practice at the thing you are asking yourself to do. Practice runs both ways.

Train the other direction in small doses. Twenty minutes on one thing with nothing else available, three times this week, then build from there. Expect it to feel bad early and expect that to pass, and treat it as conditioning rather than character.