Some people like to practice their music without the trills. They say trills mess everything up. The rhythms become unstable, the articulation uneven.
When the piece is already learned they go back and add the trills. The problem with this is not only the double effort required but also often incorrect fingering when playing without the trill.
Another, more productive way is to practice trills slowly and deliberately counting repercussions. If you mess up, slow down even more.
It is part of the piece and therefore needs to be learned at the same time as the notes.
A trill is like a salt in a dish. Take it out and it lacks flavor.